Visit the Avaiki Caves

Limestone arches over hidden pools.

Crystal coastal swimming pools.

Walk through a forest of razor coral pinnacles to a ladder that drops into a hidden sandy oasis with palm trees between the cliffs.

Drop into a limestone sinkhole of crystal-clear fresh water on the Yucatan, where the Maya saw the entrance to the underworld.

Limestone cave with a swimmable freshwater pool on Tongatapu.

Sea cave on the Algarve coast with a round skylight in its domed roof — reached by boat, kayak or paddleboard.

Sea cave at the island’s northern tip with anemone pools and ocean windows.

Humpbacks come within metres of the shore from July to October, and Niue lets you snorkel beside them.