My first guess would be that Williams couldn’t hold his breath long enough and drowned.......there’s some things that should only be done in the bedroom, not the jacuzzi.
Which begs the question, what were they doing in an empty hot tub? Surely there's a better place to sleep...
They better check the body for water in the lungs, I suspect he drowned in mid-debauch and the other men drained the tub to remove evidence (DNA)