Dolphins spray water to take a breath, because they breathe with their lungs. Unlike other marine creatures, they have no gills and cannot breathe in water. Dolphins mainly rely on their mouths and noses when they breathe. When they breathe, they will first discharge the exhaust gas in their bodies. When they exhaust gas, the gas is strong, so it will wash up the water on the water surface and look like water spray.

Dolphins have much larger lungs than humans, and they can dive for 20-30 minutes with one breath. In addition, there are some special varieties, which can last longer. But no matter how long they can last, they still need to float to the water regularly to breathe.

There are many species of dolphins, and of course some can grow in fresh water. But most dolphins live in seawater. Under normal circumstances, dolphins living in seawater cannot survive in fresh water. Because they have adapted to the marine environment, when living in the ocean, they will swallow seawater to maintain the balance of osmotic pressure in their bodies. Moreover, they have adapted to the marine environment. If they are directly allowed to move in fresh water, there may be a lot of discomfort and death.