Which animal is the fastest swimmer over short bursts?

The sailfish is the usual answer, at figures often quoted around 110 kilometres an hour - and those figures deserve suspicion. They trace back to a single mid-century experiment measuring how fast line was pulled off a reel by a hooked fish, which is not a clean measurement of anything. Careful modern work on swimming muscle and fin mechanics suggests the real ceiling for any fish is more like 40 to 50 kilometres an hour.

What is not in doubt is the equipment. Sailfish have a stiff streamlined body, a crescent tail that generates thrust with very little drag, and a huge dorsal fin - the sail - which is normally folded flat into a groove and raised for manoeuvring and for herding prey.

The hunting is the impressive part rather than the top speed. Sailfish work in groups to drive baitfish into a tight ball at the surface, then take turns slashing through it with the bill to stun individual fish, changing colour as they do - stripes flashing bright blue, which appears to signal to the others which fish is about to attack and prevents them injuring each other.