Three application of archimedes principal

1. Fish float based on Archimedes' principle. Most fish have an organ known as the swim bladder. When they want to rise, fish release gas into the swim bladder and increase their volume. As a result, they displace more water. The force of buoyancy acting on them increases. To come down, a fish empties the bladder to the required extent, reducing the volume and the force of buoyancy acting on it.

2. A hot air balloon rises and floats due to the buoyant force (when the surrounding air is greater than its weight). It descends when the balloon's weight is higher than the buoyant force. It becomes stationary when the weight equals the buoyant force.
The weight of the Hot-air balloon can be controlled by varying the quantity of hot air in the balloon.

3. A hydrometer uses Archimedes’ principle to determine the density of any liquid.