Because they need it. They can't actually breathe out of water so they need things like filters or the back of boats to make air bubbles
Fish breath underwater
I will assume you are not joking. A fish does not hold it's breath it can breathe underwater using its gills.
they have gills.
Um, with gills. . . ??
they have gills
Because you have lungs and fish have gills.
Yes there is air underwater. Water is a mix of Hydrogen (H) and Oxygen (O). Hence the name 'H2O'. Hope I helped. (also, fish filter the oxygen through their gills to breath.)
yes penguins do need air to breath underwater.
They have gills which enable them to breath underwater.
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Tortoise does not have gills to help it breath underwater.
Seahorses are fish that live underwater and breath with gills, and have fins.