"3 ... 2 ... 1 ... SLIP 'N SLIDE!!!!!"
That's how the Washington Mystics spent their first few minutes as WNBA champions ... 'cause after they beat the Connecticut Sun, 89-78, Thursday, they went back to their locker room for some champagne dives!!!
The vid is hilarious ... the team sprayed down their clubhouse with a ton of booze -- and with a protective layer of plastic laid on the ground, they decided to get down on the floor.
Shatori Walker-Kimbrough and Natasha Cloud counted backward from 3 ... dove across the carpet -- and good times were had by all.