Fish can suffocate underwater if they cannot get enough oxygen across their gills. Most fish extract dissolved oxygen from water, so low oxygen, damaged gills or blocked water flow can prevent gas exchange. The process is similar to drowning in outcome, although fish normally breathe water rather than air.
Gills extract oxygen from water
Fish move water across thin gill surfaces where dissolved oxygen enters the blood and carbon dioxide leaves it. Large surface area and continuous flow make this exchange efficient. The University of Hawaiʻi describes water passing over gill filaments and oxygen moving into the bloodstream. [1]
When underwater breathing fails
Warm water can hold less dissolved oxygen than cool water, and decaying algae or other organic material can consume oxygen. Fish may then become stressed or die in a fish kill. Some species also need to swim or actively pump water to ventilate their gills.
Some fish breathe air
A few fish can take oxygen directly from air or use specialized organs. That does not change the basic rule: each species depends on the oxygen sources and breathing system adapted to its environment.
Can a fish suffocate in water?
Yes. Water with too little dissolved oxygen or impaired gill flow can prevent it from getting the oxygen it needs.
Sources and evidence
- University of Hawaiʻi — Structure and function: Fish ↗
Explains gill gas exchange and oxygen transfer into fish blood.
- University of Florida IFAS — Dissolved oxygen for fish production ↗
Explains dissolved oxygen and how fish absorb it through gills.
Sources consulted: 11 October 2026. Written with AI assistance and checked against the linked references; not independently reviewed by a subject specialist. Sources do not endorse this article. See our editorial policy.
Revision: Initial publication; explanation checked against linked institutional and scientific sources.