[Closed] Is it easier to swim in warm water?

Mrs MTG is helping junior with her homework.
One of the things she mentioned she has learned from it herself is that as warm water is less dense, it creates less drag, so it is easier to swim through.
However, I would have thought that if the water is less dense, then to displace the same mass of water, the swimmer would float lower, creating more drag.
Do the two cancel each other out, or is there really an advantage to swimming in warm water?
What about salt water, which is denser at the same temperature? Does that make it harder to swim through than fresh water?