I made the assumption that, except in calm conditions, one's balls would usually be in motion, and therefore wetted. Not sure what capillary action of water on one's balls would be, either.
If we are trying to keep water warm, increasing its surface area by any means is a no no.
Just as saucering tea/ coffee when in a hurry.
However, I might just be wrong! Look at:
Halfbakery: Ping Pong Reservoir
All metmen know that "when I'm right no-one remembers, when I'm wrong no-one forgets.