Can you drown when you live in water?
Technically, fish cannot drown as they are able to breathe in water, but they can suffocate or be asphyxiated — drowning is simply the incorrect term. Just like humans, fish need oxygen to survive, so if there is not enough oxygen in the water they will die. Fish breathe in oxygen that is present in the water and expel carbon dioxide.
In open water like a river or the ocean, new oxygen can enter the water from the surface, but in a tank a small surface area can affect the oxygen levels, as there isn’t enough air-to-water contact to replenish the oxygen in the water. This is why aquarists use water pumps to help oxygenate the water and often why fish kept in tanks at home often die if levels aren’t kept just right.
However, it is not only fish in tanks that are at risk of suffocating. Overcrowding and gill damage could also lead to a lack of oxygen, as can the temperature of the water. Stagnant water often has less oxygen and rising sea temperatures are a major concern for the future of fish for this exact reason.