Of course, the fan-favorite giant has been using his free time in the NBA bubble to try out some new sports ... including hitting the links to golf with Orlando Magic center Mo Bamba.

The big guy is now taking on another challenge -- swimming -- and jumped in the pool with his teammates Jaylen Brown and Enes Kanter for his very own lesson.

The results are hilariously awesome ... with Kanter and Brown carrying Tacko through the pool while he works on his form.

There are no water wings in sight ... but then again, all Fall has to do is stand up in the water and he'll be good.

The Celtics have been HOT since entering the bubble and currently have a 1-0 lead on the Raptors in the 2nd round of the playoffs, so there's still plenty of time for improvement.