Do you know how heavy load on the oceans are at the moment?

 If there were no more ships in the seas, how much would the sea level rise?

Humans have filled even the boon like water with weapons of war and have made the oceans a battleground, according to one estimate , there are 10,377 ships in all world militaries, 53,732 ships in all world merchant fleets, 4.6 million fishing boats worldwide, and nearly 30 million pleasure boats. Therefore, it is almost 35 million ships across all classes.

The Seawise Giant, which can carry 657,019 tonnes, is the biggest ship ever constructed.

Credit for image: Maritime Connector

If Earth's 35 million ships were so large, they would move around 23 gigatons of matter (23x10e9). In contrast, the weight of all the water in the oceans on Earth is around 1.4 exatons (1.4x10e18). That represents a 9-order difference in magnitude.

Therefore, the volume of 23 cubic kilometres is a good match for the weight of 23 gigatons. The oceans cover 361.9 million square kilometres of Earth. The ocean would shrink by around 0.064 millimetres if this 23 cubic kilometres were distributed over the entire surface of the oceans (23/361,900,000). (about the thickness of a sheet opaper.