The living organisms that thrive in the warm, wet, Petri dish-like conditions of a hot tub (especially communal tubs). In more favorable conditions, jacooties can actually be seen floating in the froth. DO NOT assume that skimming the froth will remove jacooties from the tub.
I'm not going in that hot tub. Andrew was in there last night with two skanks and now it's full of jacooties. Look, you can see them circling in the froth.
Jacooties are those scuba diving cum bugs that live in heart-shaped jacuzzis at those rent a room by the hour motels. Jacooties prefer to hang out in the jets and wait for some nasty snatch (OR for a Jerkin' Gerkin) to come by to ride the ~~~waves~~~. At which point they will latch on to anything they can hold on to, usually the human's skin by their itchy little teeth. They especially love the warmth in the wrinkles of a ball sac while being transported to your home to explain to your spouse!
Cheating husband to wife:
"Honey, I swear i have no idea where those jacooties came from! Maybe someone brought them to the community swimming pool when i was there yesterday. Or maybe my towel was touching someone else's that has them. I swear!"
(The whole time he's panicking inwardly that he should give Janet, his girl on the side, a call to warn her of her new crotch critters)