1. Ornamental: Dolphins are common ornamental fish in aquariums, because they are naturally close to human beings, gentle in character and simple to tame. After training, dolphins can perform many programs for human beings to enhance their enjoyment.

2. Saving people: Dolphins living in the ocean often rescue people who fall into the water. When people accidentally fall into the middle, they may lift them with their beaks and leak them out of the water. Other dolphins will put humans in shallow water or shore.

3. Salvage: Dolphins can also help humans salvage objects that have fallen on the seabed. As long as humans train them, they will go to the bottom to salvage designated objects.

4. Diving: Some countries also train dolphins for military reconnaissance or underwater blasting. With the knowledge and understanding of dolphins, dolphins will play more and more roles.

1. Bottlenose dolphins: This kind of dolphin is relatively common, its color is gray-black, its IQ is relatively high, and it is easy to train. They are mainly distributed between the Pacific Ocean and the Atlantic Ocean.

2. Chinese white dolphins: White dolphins are mainly distributed in the East China Sea, but also in the Indian Ocean. Their color is pink, which is rare.

3 Pilot Whale: This dolphin is relatively large, and its body length can reach 20 feet. They have many colors, some are black and some are white. They like to live in warm waters, which are more common in low latitudes.