The Cabayugan river disappears under Mount St Paul and runs 8.2 kilometres through a limestone cave before emptying straight into the sea. It has been a UNESCO World Heritage site since 1999, and by the park's own careful wording it is only “reputed to be” the longest navigable underground river in the world. You see it from a paddle boat that starts on a beach reachable only by outrigger from Sabang, two hours by road from Puerto Princesa. The hard part is not the cave but the paperwork in front of it: the park admits at most 900 people a day, and without a Visitor Entry Permit nobody boards a boat.
- TicketsThere is no official online shop.
- Price500 PHP (about $7.96) – Entrance fee / permit, adults (conversion at 1 USD = 62.80 PHP, ECB cross-rate of 18 September 2026)
- OpenTours are scheduled daily between 8 am and 4 pm; the park gives the paddle-boat slots as 8.30 am to 3.30 pm.
- Best timeThe dry season is the dependable one.
- ClaustrophobiaThe chambers are large, in places 120 metres wide and 60 metres high, so it never gets tight.
Tickets and prices
There is no official online shop. What you need is a Visitor Entry Permit, obtained either in person at the Underground River Booking Office at Mendoza Park in Puerto Princesa – the city's own tourism page still gives the old address at the City Coliseum – or through a travel agency. Independent travellers may apply for the permit themselves; everyone in the party must register individually and show valid photo ID. Guidebooks quote a processing time of around three days and advise at least one to two days' lead time, and a month or more in high season. You pay on the day of travel, at the Sabang Wharf.
Official prices
- Entrance fee / permit, adults (conversion at 1 USD = 62.80 PHP, ECB cross-rate of 18 September 2026)500 PHP (about $7.96)
- Entrance fee / permit, young adults 13–20150 PHP (about $2.39)
- Entrance fee / permit, children 3–13150 PHP (about $2.39)
- Puerto Princesa environmental fee (all ages; also covers Honda Bay)150 PHP (about $2.39)
- Audio device, compulsory from age 1385 PHP (about $1.35); 76.50 PHP (about $1.22) for young adults
- Sabang Wharf terminal fee5 PHP (about $0.08)
- Park fees per adult, added up (500 + 150 + 85 + 5)740 PHP (about $11.78)
- Outrigger boat, Sabang Wharf to the cave beach, per boat for 6 people2,100 PHP (about $33.44) – that is 350 PHP or about $5.57 a head
- Outrigger boat for 10 people (the maximum)3,500 PHP (about $55.73) – again 350 PHP a head
- Doing it yourself: everything payable at the wharf (park fees plus your share of the boat)about 1,090 PHP (about $17.36)
- Group day tour from Puerto Princesa with transfer, guide, permit and lunch2,200–2,500 PHP (about $35–40)
- Combination package: Underground River plus zipline plus mangrove paddling tour3,550–4,920 PHP (about $57–78)
- Shared van from Puerto Princesa to Sabang, one way (guidebook figure; the city's own tourism page still says 150 PHP)about 450 PHP (about $7.17)
As of 09/2026 · source and direct booking: undergroundriver.puertoprincesa.ph
When everything is sold out
The daily cap is 900 people and it is not raised – not on public holidays, and not on 11 November, the official Underground River Day. Most of the places go to travel agencies, which draw their allocations in advance. Arriving in high season – Christmas, Easter, March to May – without a permit means finding the counter closed.
Underground River tours from Puerto Princesa
There is nothing to book direct: the park sells no tickets online, and the Visitor Entry Permit is issued in person at Mendoza Park or at the Sabang counter. So what a reseller sells you is the day itself – the two-hour transfer, the permit handling, your share of the outrigger and usually lunch, from about $35. That is worth paying for when the daily quota is tight, when you have no time to go to the booking office, or when you want free cancellation on a trip the weather can close at short notice. Check the inclusions: the 150-peso environmental fee is often left out and collected separately on the day.
From Puerto Princesa: Underground River Full-Day Trip
Puerto Princesa: Underground River, Zipline, Paddleboat Tour
From Puerto Princesa: Underground River Guided Day Trip
Puerto Princesa: Underground River Tour
Show all 7 offers
Booked through GetYourGuide (affiliate link, advertising). Most offers can be cancelled free of charge up to 24 hours ahead. Prices as of 20 September 2026.
Opening hours and best time
Tours are scheduled daily between 8 am and 4 pm; the park gives the paddle-boat slots as 8.30 am to 3.30 pm. The narrow window is deliberate: before 8 the bats are returning to the cave, after 4 they fly out, and both are meant to happen undisturbed. There are no fixed closing days, but there are weather closures – heavy rain, a high river inside the cave or a rough sea will suspend operations at short notice, as happened repeatedly in August 2026 during the south-west monsoon. The jungle trail from Sabang to the cave mouth is listed by the park as open daily 8 am to 3 pm, while the same page also states that it is temporarily closed for renovation.
When it is quietest
The dry season is the dependable one. Guidebooks put it on Palawan's west coast from November or December to May, while the park itself calls June to December the rainy season – the overlap makes December to May the safest window. What decides your day is the sea rather than the cave: with the south-west monsoon (habagat) and a swell running, the crossing to the cave beach is cancelled, and after heavy rain the river inside the cave rises enough for the park to suspend tours. Within the day, be at the Sabang Wharf as early as you can. The wait for your boat number runs from a few minutes to two or three hours, and mornings are both shorter and calmer on the water. Peak season – Christmas, Easter and March to May – fills the daily quota fastest.
Who it suits
With children
Yes in principle. Children from the age of 3 are admitted and pay the reduced permit price; under-3s are not allowed on the tour for safety reasons. Children wear the life jacket like everyone else and have to stay seated for the whole 45 minutes. The long day – two hours in a van, the wait at the pier, two boat rides – is harder on small children than the cave itself.
Minimum age
3 years.
Wheelchair
Not accessible. The only way to the cave mouth is the outrigger boat, which lands directly on the beach with no pier; you then transfer into a low paddle boat that rocks on the water. The park also advises pregnant women against the tour.
Pushchair
Not workable. You get in and out in knee-deep water, the boardwalk to the cave is damp and slippery, and there is no room in the paddle boat.
Dogs
Animals are not provided for in the national park. Anything that looks like food – and any plastic bag – attracts the macaques, and the park asks visitors to bring neither.
Claustrophobia
The chambers are large, in places 120 metres wide and 60 metres high, so it never gets tight. What is harder to take is the complete darkness between the beams of the spotlight and the fact that for 45 minutes you cannot get out. With severe claustrophobia this is not a good choice.
What to wear
Clothes you do not mind getting wet: sea water comes over the gunwale on the crossing to Sabang and on to the cave beach, and the cave roof drips. Closed water shoes or sandals with a strap beat trainers, because you step into the water at the beach. The park provides the helmet and the life jacket and both are compulsory. Bring a dry bag for phone and camera, and a cap to wear under the helmet – bat droppings fall from the ceiling.
Photography
Photography is allowed, flash is not: it disturbs the bats and swiftlets. Because the boat is moving and the only light is the paddler's spotlight, hand-held shots usually come out blurred. The photographs that work are taken at the cave mouth and on the beach in front of it.
Getting there
By public transport
Vans and buses to Sabang leave from the Irawan Eco-Terminal in Puerto Princesa and take about two to two and a half hours. Guidebooks put the van fare at around 450 PHP (about $7.17); the city's official tourism page still quotes 150 PHP for jeepney and shuttle van, which is below what is charged on the ground. Note that the departure point has moved – many pages still name the old San Jose terminal.
By car
Hire cars and scooters are available in Puerto Princesa; the road to Sabang is sealed but winding and slow. There is parking at the wharf in Sabang. Ride-hailing services such as Grab do not operate on Palawan.
From the nearest city
The park is about 76 km north-west of Puerto Princesa, roughly two hours by road – be sceptical of the “40 km” that Rough Guides and Time Travel Turtle both quote. From the Sabang Wharf a motorised outrigger crosses St Paul Bay to the cave beach in about 20 minutes; there is no pier, so you step into the water. From the beach it is five to ten minutes on a boardwalk through the forest to the cave lagoon. The alternative to the boat is the 5.3 km jungle trail from Sabang, often called the Monkey Trail – the park's own page lists it as temporarily closed for renovation, and in any case it is hot work. International visitors fly into Puerto Princesa (PPS) from Manila, Cebu or Clark in a little over an hour; the airport is about ten minutes from the booking office at Mendoza Park, which makes it practical to sort the permit on arrival day and go out to Sabang the next morning.
Tips for your visit
- Permit first, itinerary second. Without a Visitor Entry Permit nobody boards a boat, and the permit is not sold online – you get it at the Booking Office at Mendoza Park, at the counter in Sabang, or through a travel agency. In high season allow a week, and preferably a month.
- Bring passports. Every person has to register individually with valid photo ID for the permit, children included.
- Be at the wharf early. The wait for a boat number swings between a few minutes and two or three hours, and it gets longer as the morning goes on; the group tours from the city arrive in a block from about 9 am.
- Carry cash in small notes. Fees, your share of the boat and lunch are all paid in pesos on the spot; ATMs in Sabang are scarce and cards are the exception.
- Wear a cap under the helmet. Thousands of bats and swiftlets hang above the boat, and what comes down comes down. Experienced visitors look up with their mouths shut.
- Pack a dry bag. You get wetter on the crossing than in the cave – with any swell, spray comes over the bow.
- No food, no plastic bags. The long-tailed macaques along the boardwalk are used to people and will grab at bags, sunglasses and hats. Feeding them is prohibited because it makes them aggressive.
- Keep the environmental-fee receipt. The 150 pesos also cover Honda Bay, so if you have paid it there you do not pay again here – provided the receipt is still valid.
- Use the waiting time. Sabang itself has the mangrove paddling tour (around 350 PHP, about $5.57) and a zipline, and Ugong Rock is close by. Most package tours use exactly these to fill the gap.
- Check the park's site a day or two before you travel. The Sabang Wharf procedure has been in a dry run since February 2026, and bad weather closes the river at short notice.
What the internet gets wrong
The park does not claim this. Its own page says only that the river “is navigable up to 4.3 km. and is reputed to be the longest navigable underground river in the World” – navigable, and reputed. Since the 2007 survey of the Sac Actun system on the Yucatán peninsula, the English Wikipedia lists Puerto Princesa as the second-longest underground river; everything-everywhere.com is one of the few English pages that spells this out. Drop the word “navigable” and the claim stops being true.
That is the Philippine Consulate General in Los Angeles, on its own website. The underground course is 8.2 km, not 82 – a factor of ten, and “largest” is not “longest” either. UNESCO gives 8.2 km for the property, the park gives 4.3 km as navigable, and the standard tour turns round after about 1.5 km. Two other English pages inflate the tour itself: adventurersnotes.com calls it “a length of 3 kilometers”, remarkabledestination.com “approximately 4.5 kilometers of the accessible portion”.
Both sentences are on citytourism.puertoprincesa.ph, the official tourism site of the city that runs the park. In September 2026 the counter charges 500 PHP entrance, 150 PHP environmental fee, 85 PHP for the compulsory audio device and 5 PHP terminal fee – 740 PHP or about $11.78 – and the outrigger for six costs 2,100 PHP, three times the 700 quoted. The same page still gives the booking office address as the City Coliseum, which the park's own site has replaced with Mendoza Park. Travel blogs follow the authority down: journeywonders.com still bills “250 PHP plus 85 PHP of the mandatory audio guide”, “40 PHP for the environment fee” and “200 PHP for the roundtrip boat ride”, for a do-it-yourself total of “975 PHP”. A government page that does not know its own prices is the root of most of the wrong numbers in English.
Adventurersnotes.com still publishes the old boat tariff in full, and thebrownetown.com reports paying “200 pesos to share the boat with 7 others”. Current guidebook figures are 2,100 PHP for a boat of six and 3,500 PHP for a boat of ten, which works out at 350 PHP – about $5.57 – per person either way. Philippine media have reported a city ordinance raising the per-head share from 200 to 350 PHP; we could not open the original report, so what is documented here is the tariff, not the ordinance.
The park has published a notice of its own against exactly this. It gives “formal notice to the public not to be mislead by pronouncements posted in the internet and other medium that going directly to the Park or staying overnight in Sabang is a guarantee for the issuance of a Visitor Entry Permit”, and says it has authorised nobody to make such commitments. The cap is 900 visitors a day and “A NO PERMIT, NO ENTRY POLICY is strictly enforced”. Walk-up permits at the Sabang counter do exist when the quota is not exhausted – they are a chance, not a plan.
That is how the Wildlife Institute of India's Conservation-to-Coexistence portal dates the World Heritage listing, and the 1997 date turns up in English-language summaries elsewhere. The park was inscribed on 4 December 1999, at the 23rd session of the World Heritage Committee, under criteria (vii) and (x). The 1999 confusion is easy to make: Proclamation No. 212, which enlarged the park to 22,202 hectares, was signed on 16 November 1999, three weeks before the inscription.
As though the two were the same kind of honour: they are not. The World Heritage inscription of 4 December 1999 is the official one, decided by the World Heritage Committee against published criteria. The “New 7 Wonders of Nature” came out of a campaign by the private New7Wonders Foundation, decided by internet and SMS voting in which multiple votes were not excluded and for which the then Philippine president publicly urged the country to vote en masse. UNESCO has nothing to do with the title.
there is no fixed lighting in the cave at all. Light comes only from the boatman's handheld spotlight, aimed at one formation at a time, and between those beams it is completely dark. Flash is prohibited because it disturbs the bats and swiftlets.
History in brief
- In 1887 the American zoologist Dean C. Worcester noted on a journey through Palawan that there were reports of a lake opening to the sea through an underground river – the earliest written trace the park management knows of. Who first entered the cave is not recorded.
- On 26 March 1971 Proclamation No. 835 declared an area of 3,901 hectares the St Paul Subterranean National Park.
- On 16 November 1999 Proclamation No. 212 enlarged the park to 22,202 hectares so that the whole catchment of the underground river was protected, and gave it its present name.
- On 4 December 1999 UNESCO inscribed the park on the World Heritage List under criteria (vii) and (x).
- Since 1992 the City of Puerto Princesa has administered the park – the first national park in the Philippines handed over to a local government unit.
- In 2010 an expedition of environmental specialists and geologists established that the cave has a second storey with small waterfalls; they also documented a dome some 300 metres high above the river, a deep water hole and further passages. The deeper sections are barely explorable because of the lack of oxygen.
- On 11 November 2011 the private New7Wonders Foundation provisionally named the river one of the “New 7 Wonders of Nature”; the result was confirmed on 28 January 2012.
- On 30 June 2012 the park was added to the Ramsar list of wetlands of international importance.
- Since 7 February 2026 the park has been trialling a new guest-handling procedure at the Sabang Wharf.
Frequent questions
Do you need a permit for the Puerto Princesa Underground River?
Yes, and nothing happens without one. The park enforces a “no permit, no entry” rule because at most 900 people a day are admitted. The Visitor Entry Permit is issued at the Underground River Booking Office at Mendoza Park in Puerto Princesa, at the counter at Sabang Wharf, or through a travel agency. There is no official online sale.
How far in advance should I get the permit?
Guidebooks reckon on about three days' processing and advise at least one to two days' lead time. In high season – Christmas, Easter and March to May – the quota is often gone a month ahead. Independent travellers may apply themselves, but need photo ID for everyone in the party.
How much does it cost to visit the Underground River?
At the counter in Sabang an adult pays 500 PHP entrance, 150 PHP environmental fee, 85 PHP for the compulsory audio device and 5 PHP terminal fee – 740 PHP, about $11.78. Add your share of the outrigger at 350 PHP, about $5.57, and you are at roughly 1,090 PHP or about $17 (1 USD = 62.80 PHP, ECB cross-rate of 18 September 2026). Transport and lunch are extra.
Can you book Underground River tickets online?
Not with the park. The permit is issued in person or by an agency, and there is no official ticket shop. What you can book online is a tour – the transfer, the guide, the lunch and the handling of the permit. Read the inclusions closely: the 150-peso environmental fee is often left out and collected separately on the day.
Can you visit the Underground River without a tour?
Yes. Take a van from the Irawan Eco-Terminal to Sabang, register at the wharf, pay the fees, join an outrigger and go. It works if you already hold a permit, or if you are at the counter early on a quiet day. The park says plainly that turning up without one – even after a night in Sabang – guarantees nothing.
How long is the boat tour inside the cave?
About 45 minutes, up to an hour on some boats. It covers roughly the first 1.5 km, although 4.3 km is navigable; beyond that the boats no longer fit through the narrows, and going further needs a special permit from the national park office. With the drive, the wait and the return, the outing fills a whole day.
How do you get from Puerto Princesa to Sabang?
Vans and buses from the Irawan Eco-Terminal cover the 76 km in about two to two and a half hours, at roughly 450 PHP for the van. Self-drivers take a hire car or a scooter; Grab does not operate on Palawan. From the Sabang Wharf it is another 20 minutes by outrigger across the bay.
Is the Underground River suitable for children?
Children from 3 can go, younger ones cannot. They pay the reduced permit price of 150 PHP, wear a life jacket and stay seated throughout. The cave is the easy part – the two-hour drive, the wait at the pier and two boat rides are what wear small children out.
What should I wear and bring?
Clothes you do not mind getting wet, and water shoes or sandals with a strap, because you step into the water at the cave beach. The park supplies the helmet and life jacket and both are compulsory. Add a dry bag for phone and camera, cash in small notes, and a cap under the helmet against bat droppings.
Is the cave lit inside?
No. There is no installed lighting. The boatman works a handheld spotlight and picks out one formation at a time; in between it is entirely dark. That is also why photographs rarely come out – the boat is moving and flash is banned.
Are there bats, and do they bother you?
Eight bat species live in the cave and the boat passes directly underneath them. Droppings coming down are normal – hence the helmet, a cap underneath and the standing advice to keep your mouth shut when you look up. The bats themselves take no interest in the boats.
What is the best time of year to visit?
December to May. The sea is calm enough for the crossing and the river inside the cave is low. During the south-west monsoon from June to October tours are cancelled at short notice; in August 2026 the cave was shut for days at a time.
Can you walk to the cave instead of taking the boat?
In principle yes: a 5.3 km jungle trail, widely called the Monkey Trail, runs from Sabang to the cave mouth and is officially listed as open 8 am to 3 pm. The same park page also states that it is temporarily closed for renovation, with no date. Ask the park or your operator before you travel, and bring walking shoes, water and insect repellent either way.
Is the Puerto Princesa Underground River worth it?
If you like caves, you get something with few equals: a navigable river running under a limestone massif straight into the sea, through chambers up to 120 metres wide and 60 metres high. If you are expecting a lit show cave, you will be disappointed – it is dark, noisy on the way in and slow to organise. The 45 minutes in the boat are a small part of the day.
How many steps are there?
None. There is no staircase anywhere on the route. You step from the outrigger into knee-deep water, walk five to ten minutes on a level boardwalk through the forest, and transfer into the paddle boat at the lagoon. The physical demands are the transfers and sitting still, not climbing.
Sources
Show 34 sources – every figure on this page is sourced
- undergroundriver.puertoprincesa.ph/ – Official site of the park management: paddle-boat slots 8.30 am–3.30 pm, tours daily except in extreme weather
- undergroundriver.puertoprincesa.ph/notice-to-the-public/notice-… – Notice to the public: “not to be mislead by pronouncements posted in the internet … that going directly to the Park or staying overnight in Sabang is a guarantee for the issuance of a Visitor Entry Permit”, cap of 900 visitors a day, “A NO PERMIT, NO ENTRY POLICY is strictly enforced”, tour hours 8 am–4 pm
- undergroundriver.puertoprincesa.ph/travel-advisory/travel-advisory-2/ – Reason for the daily cap (bats and swiftlets), address of the Underground River Booking Office at Mendoza Park with phone number and the note that it is ten minutes from the airport, requirement to present valid ID and register individually
- undergroundriver.puertoprincesa.ph/points-of-interest/ – “It is navigable up to 4.3 km. and is reputed to be the longest navigable underground river in the World”, one-hour paddle-boat tour, 5.3 km jungle trail open 8 am–3 pm and at the same time “Temporary closed for renovation”, other caves in the park
- undergroundriver.puertoprincesa.ph/wonders-of-nature/ – How the paddle-boat tour runs, licensed boatmen, cancellation in extreme weather
- undergroundriver.puertoprincesa.ph/new-7-wonders-of-nature/ – Date of the New 7 Wonders of Nature vote (11 November 2011) and the other six winners
- undergroundriver.puertoprincesa.ph/world-heritage-inscription/ – World Heritage inscription on 4 December 1999 under criteria (vii) and (x)
- undergroundriver.puertoprincesa.ph/physical-features/ – Karst 11 km long, 3–5 km wide, 35 km², 16–20 million years old, Mount St Paul 1,028 m, the Cabayugan river as the feeder
- undergroundriver.puertoprincesa.ph/biodiversity/ – Eight bat species in the cave, 165 bird species, 800 plant species, macaques and monitor lizards, cave fauna
- undergroundriver.puertoprincesa.ph/news/public-advisory/ – Dry run of a new guest-handling process at Sabang Wharf from 7 February 2026, published as images only
- puertoprincesa.ph/underground-river/ – City page: 8.2 km underground river, brackish water and tidal influence, Proclamation 835 (1971) and 212 (1999), park area 22,202 ha, distance 76 km, discovery of the second storey in 2010 with a 300 m dome, climate (rainy season June–December, 29 °C), Worcester 1887
- citytourism.puertoprincesa.ph/ppur/ – The city's own tourism site, with out-of-date prices – “Secure entry permits (which costs Php 175 - Php 250) from PPUR booking office” and “Pump boats ferry visitors from Sabang Wharf to the Park … it costs Php 700.00+ good for 6 persons capacity”, jeepney and shuttle van at “Php 150.00+ per person”, and the old booking office address “PPUR Office, City Coliseum Bgy. San Pedro”
- whc.unesco.org/en/list/652/ – UNESCO brief description, 8.2 km river flowing directly into the sea with tidal influence, chambers up to 120 m wide and 60 m high, about 76 km north-west of Puerto Princesa
- en.wikipedia.org/wiki/Puerto_Princesa_Subterranean_River_Nation… – Second-longest underground river in the world after the 2007 Yucatán survey, cave system at least 32 km, Italian's Chamber 360 m, salt water up to 6 km in, criticism of the New7Wonders vote, Ramsar site since 2012
- everything-everywhere.com/puerto-princesa-subterranean-river-na… – English-language page that states the distinction correctly: “inscribed by UNESCO in 1999”, “the longest navigable underground river in the world”, and that an underground river on the Yucatán peninsula took the outright record in 2007
- losangelespcg.org/the-puerto-princesa-subterranean-river-nation… – Evidence for two English-language errors on an official Philippine government page (Consulate General, Los Angeles): “Approximately 82 kilometers long, the park's river is the second-largest underground river in the world”, and the World Heritage listing and the New 7 Wonders title presented side by side as equivalent honours
- c2c.wii.gov.in/puerto-princesa-subterranean-river-national-park – Evidence for the English-language error “inscribed in 1997” on the Conservation-to-Coexistence portal of the Wildlife Institute of India; the page also gives the national park declaration of 26 March 1971 correctly
- www.journeywonders.com/the-puerto-princesa-underground-river/ – Evidence for several English-language errors: “250 PHP plus 85 PHP of the mandatory audio guide”, “40 PHP for the environment fee”, “200 PHP for the roundtrip boat ride”, a do-it-yourself total of “975 PHP”, and “flash photograhy is allowed at the Puerto Princesa Underground River”
- adventurersnotes.com/my-blog/philippines/puerto-princesa-underg… – Correct on the current fee chain (₱500 entrance, ₱85 audio device, ₱150 environmental fee, ₱5 terminal fee, ₱740 total, and the reduced rates for 13–20s and 3–13s), but evidence for the outdated boat tariff “6 people (total capacity) – ₱1100 – ₱184 per person”, “8 people – ₱1425 – ₱179 per person”, and for a tour length of “3 kilometers”
- thebrownetown.com/underground-river-diy-guide/ – Evidence for the outdated boat share: “200 pesos to share the boat with 7 others, bringing my total cost to 935 pesos” and “Php1,425.00” for a boat of eight; also the 900-a-day cap, a 45-minute tour and a quoted 300 pesos for the jungle trail
- www.roughguides.com/article/puerto-princesa-underground-river-p… – Evidence for the distance error “about 40km (24 miles) north of Puerto Princesa City” and for an outdated boat price “₱1,000 ($18) for a shared boat”; correct on “the longest navigable underground river in the world” and on the permit requirement
- www.timetravelturtle.com/philippines/puerto-princesa-undergroun… – 2026 guide, correct on “the longest navigable subterranean river in the world”, about 1.5 km of the river on the tour and 45 minutes, torches rather than installed lighting, bat droppings; evidence for the distance error “Sabang (40km from Puerto Princesa)”
- www.willflyforfood.net/underground-river-puerto-princesa-palawan/ – Permit requirement and the ratio of demand to quota (“Of the approximately 1,200 daily entry permit requests, only a maximum of 900 are granted”), tour covering the first 1.5 km, “pitch black inside, save for the small beam of light from the boat's spotlight”
- www.travel-palawan.com/underground-river-travel-guide/ – 2026 guide: 8.2 km river, two-hour drive to Sabang, 45-minute paddle-boat tour, “A strict ‘No Permit, No Entry' policy is enforced”, valid ID and individual registration
- www.remarkabledestination.com/blog/puerto-princesa-underground-… – Source for the 2026 modernisation plans (digital booking system, fibreglass and electric boats, Sabang Integrated Wharf Project) that could not be confirmed by the park; also evidence for the overstated tour distance “approximately 4.5 kilometers of the accessible portion”
- seasia.co/2026/02/20/the-underground-river-navigating-the-labyr… – February 2026 article: “one of the longest navigable underground rivers in the world”, chambers up to sixty metres high, “dark chambers illuminated by handheld lights”, UNESCO 1999 and New7Wonders presented together
- thepinaysolobackpacker.com/puerto-princesa-underground-river/ – Fee breakdown 500/85/150 PHP, boat tariffs 2,100 PHP for six and 3,500 PHP for ten, permit locations Mendoza Park and Sabang Wharf with opening hours, compulsory helmet and life jacket, bat droppings, waiting times of two to three hours, travel via the Irawan Eco-Terminal
- lakbaypinas.com/puerto-princesa-underground-river-travel-guide/ – Price table by age group including the 5 PHP terminal fee, processing time of about three days, cap of 900, flash ban, 4 pm close because of the bats, audio device languages, dry season, package prices, Underground River Day on 11 November
- postcardsfromtheworld.com/puerto-princesa-underground-river/ – First-hand account: permit at the counter in Sabang, compulsory audio device, cathedral chamber over 60 m high, swell and spray on the crossing, macaques on the boardwalk, bat droppings
- philippinetravels.ph/underground-river/ – Fees 500/150/85/5 PHP, boat prices per boat, tour turning round after about 1.5 km, the sequence at the Sabang boat terminal
- sanitastoday.com/puerto-princesa-underground-river-travel-guide… – Shape of the day, crossing of 15–20 minutes, 8–10 people to a paddle boat, tour of 45–60 minutes, notes for older visitors and children
- www.taraletsanywhere.com/puerto-princesa-underground-river-palawan/ – Standard tour 1.5 km, special permit for the full run, children under 3 not admitted, cave system given as 24 km, cathedral chamber, waiting time of one to two hours
- www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml – ECB euro reference rates of 18 September 2026: 1 EUR = 71.972 PHP and 1 EUR = 1.1460 USD, giving the cross-rate of 1 USD = 62.8028 PHP used for every dollar figure here
- www.xe.com/currencyconverter/convert/?Amount=1&From=USD&To=PHP – Cross-check: 1 USD = 62.9058 PHP at 14:52 UTC on 20 September 2026