Life-guarders
If you take the world press for the last several centuries you'll find a lot of interesting facts about dolphin-rescuers. There is an interesting story that happened to passengers of American plane that had the aircraft. The crew managed to survive, but they fell down into the water, they had all necessary equipment including inflatable boat. Sharks appeared at once smelling the blood. And when pilots were thinking what course to choose, a dolphin appeared. It began to save people pushing the boat to the nearest island.
Another not less thrilling story happened during the World War 2 when the soldier was saved by dolphins when he suffered from sea mine. In fact dolphins carried him being in blood to the sand bar.
Once the passenger ship sank, and there were a few people who managed to survive, but when they saw sharks they lost any hope. Suddenly dolphins appeared and made sharks go away helping people not to sink till the appearance of rescuers.