"floating under the influence"; floating on a tube or
raft down a body of water, prefferably a fast moving river, while
shitcanned (i.e. wasted or
fucked-up on any drugs)
Yesterday, while
tubing down the mighty
Mississippi, Jimmy got a FUI for being intoxcated while flashing his "down-stairs
mixup" to the police; his wasted ass went to jail.