Speed-Swimming is the ability all mermaids and mermen are shown to have. It is one of the most used merpeople abilities in H2O: Just Add Water and in Mako Mermaids. It allows them to swim at the speed of 600 km/h. Their body is encased in bubbles and use it as a jet stream to swim faster. This power is mostly used for racing other merpeople or escaping from boats and other merpeople. It is also used to get somewhere faster if they're upset, angry or are just doing it for fun. it some cases it can be called a torpedo the first thing i could find was in the Netflix description for close call.