What is the fastest a dolphin can swim? Near the surface, no more than 54 kilometres per hour. Why? Because it hurts them to swim faster.
When a dolphin swims really fast, it’s tail beats very fast. When this happens tiny bubbles form around the tail like the bubbles that stream behind a ship’s propeller.
When the bubbles collapse, they produce a shockwave, which eats away the metal in propellers. To dolphins, it is painful. According to the researchers’ calculations, within the top few metres of the water column, this happens when the dolphins reach 10 to 15 metres per second (36 to 54 kilometres per hour). Read more here.