Why a ship doesnt sink in the sea but floats as it is very heavy

Dear student

The amount of water it displaces (shaded area) weighs as much as theship. The weight of the ship pulling down (red arrow) and the upthrust pushing up (blue arrow) are equal and opposite forces, so the shipfloats.

Regards
Arun (askIITians forum expert)

When the ship weighs less than the maximum volume of water it displaces, then it floats. The ship floats as long as the ships weight and the upthrust equals. If the weight increases beyond the upthrust balance force, the it sinks. The upward thrust is  also called as byouncy. The ship will float as long as the density (which is weight divided by volume) is less than the water.