When humans are in trouble at sea, dolphins intervene and come to the rescue.  From the award winning 1999 BBC documentary series "Supernatural".

In two similar incidents, one in 2004 and one in 2007, pods of dolphins circled imperiled surfers for over thirty minutes in order to ward off aggressive great white sharks. And in 2000, a fourteen year old boy fell off a boat in the Adriatic Sea and nearly drowned before being rescued by a friendly dolphin. The marine mammal swam up alongside the boy and pushed him back to the boat from which he had fallen, where the boy's father promptly scooped him up. Far from being merely a modern phenomenon, historical accounts show that dolphins have been saving humans for centuries. In the 1700s, a pod of dolphins helped rescue Vietnamese sailors when their boat was sunk by Chinese invaders. According to the Whale and Dolphin Conservation Society, recorded stories of dolphins protecting humans date back to ancient Greece.