How did swimming started?

Answer 1

Swimming started by someone in the Stone Age getting into the water for a common purpose (either to bathe, catch fish, or cool off) and needed or wanted to try to transport themselves to another location in the water. (They probably used the same technique to learn how to row boats) They then painted themselves and/or other people swimming on cave walls.

Answer 2

well... some ancient dude 25000 years ago fell in the water. and he thought.... "dang I really need to get out of this water." and thats how it all began.