When a boat is kept on water surface, the presure of water pushing up on the bottom of the boart
and bady remain afloat by an upwards force (buoyant force). As the boat slowly lowered into the water,
due to increase in buoyant force it displaced more and more water.
The boat will stop sinking once the buoyant force become equal to the weight og liquid displaced by the boat.
This is how body floats in water.