When you ejaculate into a belly button (your own or someone else's) and then another person uses a straw to blow bubbles into it, hence a tiny nasty jacuzzi.
Now, if they drink it, well that's a whole new thing.
-Dude, Barbara and I did a Nasty Jacuzzi yesterday.
-WOAH, Who made the bubbles?
-I'd never tell.
When a couple sets up in 69-form, the lady sets her asshole on his nose, urinates in his mouth, and uses the force of her flatulence to send air bubbles through his nasal passage and cause the urine in his mouth to bubble, a la jacuzzi
Your momsaid she wanted to go hot tubbing last night. I said "Nah, lets hit the jacuzzi instead."