Question

why does it happen a ship dips to a layer debt in water will sink or come to the surface of water

Answer 1

Fresh water has a density of about 1000 kg/m cube.

Sea water has a density of about 1025 kg/m cube, because of the dissolved salt and other materials in it .

Salt water is denser than fresh water. So,salt water provides more buoyancy than fresh and because of this ship dips to larger depth in fresh water.

The density of ocean surface depends on other factors also like pressure, temperature , and dissolved gases. Different ocean have different density depending on its origin.Density given above is the approximated one.