Dolphins can still give Phelps a lesson

Dolphins have a kick that would make Olympic gold-medalist Michael Phelps jealous of 96 kg worth.

How dolphins are able to swim so fast first preoccupied researchers back in 1936, when zoologist James Gray calculated the drag dolphins must overcome to swim faster than 32 km an hour. Gray said dolphins lacked the muscles to swim so fast, and yet they did. This became known as Gray's Paradox.

Gray theorized that their speed possibly had something to do with their skin. Over the decades, scientists found flaws in Gray's work, and most biologists have rejected his theory.