Humpback whales are enormous — a fully grown adult can be 15 metres long, about the same as two double-decker buses parked end to end — but they are famously calm and curious. In Tonga's warm, clear water, mother whales rest near the surface while their calves practise swimming and breathing. The calves are playful and sometimes roll and spin right in front of snorkellers, as if they are showing off.
What makes Tonga extra special is the singing. Male humpback whales sing long, complex songs that can last for hours. Scientists are not entirely sure why they sing, but the songs change a little each year, and all the males in the same ocean gradually learn the latest version — like a slow, underwater hit song spreading across the Pacific. In the water you can hear the song coming through from far away, a deep moan that vibrates through your whole body.
Strict rules protect the whales when people swim near them. Swimmers must not touch the whales, must not chase them, and must let the whales decide how close they want to come. This respectful approach means the whales are comfortable in Tongan waters and keep returning year after year. It is one of the most extraordinary wildlife experiences anywhere on Earth.