How Do Animals Breathe Underwater?

Animals living in the water have adapted their respiratory systems to the environment with a few stunning tricks.

Most animals that live in the water have gills. Yet, many mammals, birds, insects, amphibians and reptiles also live in the water and dive to get some food. They have lungs, which are not suited to breathing underwater. But how do they survive in the water then?

• How do Sea Mammals (e.g. Dolphins and Whales) Breathe Underwater?

Mammals such as seals, sea cows and sea otters cannot breathe underwater, because they do not have gills. They have to return to the water surface regularly.

Dolphins and whales have specifically adapted their respiratory systems to their environment. They do not breathe through their mouth, but use breathing holes at the top of their heads. The advantage: They only have to come up so far that their breathing holes are above the water surface. They first exhale the used air through the breathing hole.

This often causes a little fountain, as there normally is some water left in the breathing hole from diving up. Then they breathe in through the open breathing hole and close it again before diving into the sea again.

Humpback Whale Humpback Whale - Photo: Ethan Daniels/Shutterstock

• How do Amphibians (e.g. frogs) Breathe Underwater?

Amphibians have lungs, but can only breathe with their skin - frogs for instance. When underwater, they breathe with their skin. On land they use their lungs.

Leaping Frog Leaping Frog - Photo: Eduard Kyslynskyy/Shutterstock

• How do Reptiles (e.g. Turtles and Crocodiles) Breathe Underwater?

Reptiles have lungs and therefore have to return to the water suface regularly.. Crocodiles have – similar to whales and dolphins – adapted to their habitat: They exclusively use their nostrils to breathe. When lying in ambush, you can often only perceive their nostrils protruding out of the water.

The Fitzroy river turtle (rheodytes leukops) has developed a rather unusual method: It breathes ... with its bum! This is possible thanks to the extremely delicate cell tissue of its cloaca (the body opening for the intestines and genitals).

Hawksbill Sea Turtle Hawksbill Sea Turtle - Photo: Rich Carey/Shutterstock

• How do Insects Breathe Underwater?

Insects have tracheae and have to return to the water surface to breathe.Yet, many water insects have cleverly adapted to this habitat and developed several strategies: Some of them “snorkel” for instance by lifting only the part of the body with the breathing holes out of the water – like wigglers or the water scorpion.

Other animals just take the oxygen down with them. Little air bubbles “stick” to the tiny hairs on the back of the diving water spider for instance.

• How do Fish Breathe Underwater?

Fish do not have to return to the water surface. They have gills, to absorb the oxygen from the water. Here are some interesting facts about the oxygen in the water: It is not easy to absorb the oxygen from the water when diving. The air contains about 30 times as much oxygen as water. The warmer the water, the smaller the amount of oxygen it contains.

There are several species of fish that can cope with high water temperatures – such as the pupfish that can even survive water temperatures of up to 40 degrees Celsius. Most fish feel much better in colder water, as it contains more oxygen. Yet, there is no temperature that applies to all fish (compare the Arctic Ocean and tropical seas).

How Important is the Water Temperature?

The colder the water, the more oxygen is contained in it. Why? In warm waters the oxygen particles are more agile. Thus it is easier for them to leave the water. In cold waters, the oxygen particles are less agile and cannot “escape”.

Try this: Watch boiling water for instance.