To Sua Ocean Trench on the south coast of Upolu Island in Samoa

© Chris McLennan/Alam

An inland ocean. To Sua Ocean Trench

This majestic swimming hole on Samoa's Upolu Island sits just inland from the Pacific coast. It was formed when the roof of an ancient lava tube collapsed, exposing the 98ft deep pool. This is the largest of many such tide pools and blow holes formed in the area many thousands of years ago. An underground cave system connects this swimming hole to the nearby ocean, and the water rises and falls with the tides.

To Sua means “big hole” in English which, while accurate, feels like a bit of an understatement. For adventurous visitors to Upolu Island, a visit to To Sua Ocean Trench can feel otherworldly. To get to this natural saltwater pool, you have to make your way along a cliffside path surrounded by lush forest. Then climb down the wooden ladder to the water. After your swim, you can squeeze through a cave-like lava tube to find yourself on a short, sandy beach.