The world-renowned Underground River in Puerto Princesa, Palawan, was built by nature for over 30 million years.

Water coursed through the karst limestone mountains, seeping into cracks and crevices, creating passageways, tunnels, and trenches.

One of the world’s New 7 Wonders of Nature, the Underground River was carved not just from these passages of fresh water. It’s also heavily influenced by the tides in the sea.

Because the Underground River is situated next to the West Philippine Sea, the water in the tunnel is brackish, a combination of saltwater and freshwater.

During the amihan season or the northeast monsoon between November and March, the tides from the sea cause waves and currents in the Underground River.

When this happens, there is a 10 to 20% chance of cancelled tours to the Underground River.

The only alternative to get to the mouth of the Underground River is by trekking through a forest trail, which lasts about two hours.

To minimize the risks, it’s best to consider visiting the Underground River between March and June, when the tides are calm and the weather is dry.

READ: See weather at the Puerto Princesa Underground River.