On a night-time dive near Hawaii, 2 divers were found by a bottle-nose dolphin and it started to swim around them over and over again. When looking closer, one of them discovered the reason for this strange behavior, the dolphin had a fishing line hooked around it, hindering its ability to swim.
They cut him free, and the dolphin swam away. The fact that a dolphin would come to humans for help maybe evidence of its' intelligence, as most injured animals would never come close to a human. This is amazing to watch and a life-time experience for those two divers.