Question

why it is easier to swim in sea water rather than in river or lake

Answer 1

Probably because of the salt present in the sea.

Answer 2

It is easier to swim in sea water rather than in river or lake because sea water is denser than lake or river water so it is easier to float on sea water. Because sea water will exert greater upthrust which will make it easier for us to swim.

Hope it helps you !!!