Agree. As kids, we'd swim in the Atlantic ocean, off the N.H. coast, and never got sick. I'm guessing that water, in summer, was 65F to 72K. Brrrrr... Loved it.

Grandkids swim in our 25C/77F pool water early in the season before the sun (and later our pool furnace) heats it up. My wife and I require 84F at a minimum.