Question

Dolphins and whales open come up to the water surface

Answer 1

We all know that all and most mammals breathe through their lungs. Dolphins and whales are mammals. The odd thing is that they live in water. Lungs is used for breathing air present on the surface while gills are used to breathe in the air dissolved in water. As whales and dolphins breathe through lungs they cannot breathe the oxygen dissolved in water . so they come to the water surface to take in oxygen.

The another reason is that they might want to take a look of their surroundings.

Or they simply come to the surface of the water and make huge leap just for the sake of enjoyment or they just want to do so...