gill

A gill is a respiratory organ that allows fish and other aquatic animals to breathe underwater. Gills are made up of thin, feathery structures that allow oxygen to diffuse from the water into the bloodstream.

Gills are located on the sides of the fish's head. They are covered by a flap of skin called the operculum. The operculum helps to protect the gills and to keep water flowing over them.

When a fish breathes, it opens its mouth and takes in water. The water flows over the gills, and the oxygen diffuses into the bloodstream. The blood then carries the oxygen to the rest of the body.

The fish used its gills to extract oxygen from the water.