The least weasel weighs about as much as a chocolate bar, hunts things bigger than itself, and almost never sits still. A small animal with an enormous appetite.

The animal that eats tens of thousands of ants a day, has no teeth at all, and runs cooler than almost any other mammal. Meet the anteater.

Four identical babies every time, a shell made of bone, and a startled jump that lands them in trouble. The armadillo is stranger than its quiet trundling suggests.

I told my Year 4 class that a whale's heart can weigh more than all of them added together. They did not believe me. (They should have.)

I told my Year 4 class that dolphins have names for each other. They spent the rest of the afternoon inventing whistles. (Fair enough.)

Three hearts, ten arms, and the biggest eyes on the planet. Squids are stranger than any fish, and one of them quietly helped rewrite how we understand the brain.

Sharks have no bones, hunt with a sixth sense, and some outlived the last three ice ages. Here is the useful, slightly strange version.

Three hearts, blue blood, and a brain in every arm. Octopuses are the closest thing we have to an alien, and they live in the sea, quietly ignoring us.

Creatures with no brain, no heart and no bones, older than the dinosaurs, and somehow still running large parts of the ocean. My Year 4 class adore them.

Crabs step sideways, wear their skeleton on the outside, and taste the world with their feet. Here is what years of aquarium visits taught me about them.

Once so common it was fed to prisoners, the lobster turns out to be one of the sea's oddest animals: blue blood, teeth in its stomach, and mismatched claws.

I have met shrimp at aquariums and on ice at the fishmonger. Both settings undersell them: bubbles hot as the sun, hearts in the head, and a relaxed attitude to sex.