The Camp I worked at has several acres on a lake-shore.  They were gifted to my diocese decades ago for use as a youth camp.

dock in evening

It’s a big lake, and thus rather chilly most of the year.  But as the summer continues the lake gets warmer and the days get hotter, more and more days end like this: with a camp-wide invitation to jump into the lake.  Most, if not all, of the campers get in and the lifeguards will often rotate so that any of the staff who want to can also cool down.