How does a fish float

The principle that the fish can float is in fact the famous Archimedes principle, which is the principle of buoyancy. That is, the buoyant force is equal to the weight of an object discharging the same volume of liquid.

The fish float is actually due to the expansion of the gas inside the float, so that in addition to its own volume to eliminate the buoyancy of the liquid generated, but also increased the amount of liquid discharged, that is to say, increased buoyancy, so the fish in the water can be very easy to swim.

The pressure of the water increases with the depth of the water, and the buoyancy of the water increases accordingly when the pressure increases. When the fish wants to descend to the deeper layer of water, as the pressure of the water increases, then the swim bladder contracts, the specific gravity of the fish body increases and the fish sinks.

When rising, the swim bladder expands, the specific gravity of the fish body decreases, and the fish is able to float to the surface. Whether it is rising or falling, or staying, the process of inflating and deflating the swim bladder is carried out slowly, this is because the capacity of variable gas is limited, and thus the fish can not rise or fall rapidly in the water, otherwise it will be life-threatening.