Question

What can be the highest density in seas, rivers and oceans?

Answer 1

The ocean water is most dense. Sea water is less dense, and river water is least.

Pure water has density of 1000kg/m^3.
Ocean water has a lot of salt dissolved in it, so the density increases. The density is between 1027 to 1050 kg/m^3 in ocean.

Seas have lesser dissolved salts. So density is 1020 to 1030 kg/m^3.

Rivers have nearly pure water. So, the density is near to 1000 to 1010 kg/m^3.

So, density is most in oceans, due to salt dissolved in water.

The highest density is seen in dead sea, which is 1240 kg/m^3.