Whale species

Rae Gill is the tour director of our supplier WhaleSwim Adventures. They take people swimming with humpback whales in Tonga: "Humpback whales are the most active whales. They jump out of the water - that's known as breaching - they flap their fins, flap their tails. They have to surface to breathe, as all whales do. But they're also baleen whales, which means they don't have any teeth. All baleen whales migrate because they have to go to colder waters to get their food - tiny crustaceans known as krill. So it's usually in the breeding season that the whale watching takes place for humpbacks, because that's when they migrate away from the extreme regions, like Alaska. During the breeding season they stay put for three or four months in warmer waters before making the big swim back to the Arctic or Antarctic for feeding.

Even though they're huge, humpbacks don't eat when they're in Tonga. They eat big mouthfuls of krill, and put on all this blubber in the feeding season, then go off to have babies."

In the wild, however, orcas have never been known to attack humans, and in many places you can even kayak alongside these spectacular cetaceans. Despite being known as "killer whales", orcas are actually dolphins.

Blue whales are the giants of the planet, yet for something as large as three double-decker buses, they're astonishingly hard to see. Sadly, this is due to them being hunted.

A blue whale can weigh up to 200 tons - with newborn calves weighing up to four. The adults' hearts are the size of a small car. The calf drinks an astonishing 50 gallons of milk each day - an especially impressive feat when you consider that the mothers only feed on tiny crustaceans and fish for up to four months of the year, in the colder polar regions favoured by krill and plankton, before migrating thousands of kilometres towards the tropics to give birth in warmer waters. The calves grow rapidly on the rich milk, to ensure they put on enough blubber to survive back in the colder, iceberg-filled waters.