Forget poppin' bubbly, the Illinois men's basketball team got in a water gun fight to celebrate its big Sweet 16 win on Thursday ... and the celly got so wild, head coach Brad Underwood actually ditched his top for it!
The H2O battle happened just minutes after the Fighting Illini pulled off a 72-69 upset win over No. 2-seeded Iowa State in the NCAA tournament.
Underwood -- sans tee -- kicked off the war by busting through a curtain with his staff and blasting a giant super soaker on his players.
Quincy Guerrier, Max Williams, AJ Redd and the rest of the dudes came prepared, though, and returned fire with their own smaller water pistols.