Hanauma Bay Oahu, Hawaii

For a first-time snorkeller in tropical waters, it might seem like a psychedelic dream: a cloud of black-masked raccoon butterfly fish in brilliant yellow flitters by, followed by a swarm of black-and-white Hawaiian damselfish hovering close to their favourite coral head, while parrot fish in green, yellow and orange dart in and out. Welcome to Oahu’s most popular snorkelling spot, Hanauma Bay Nature Preserve, with its picture-perfect 2,000-foot crescent-shaped beach bordered by palm trees.