Everyone has just finished changing out of their casual clothes into their swimsuits. They put on their BCDs, their masks, their weight belts, their oxygen tanks, their pony tanks, and their fins. Then Aizawa explained what getting bent is

Aizawa: shakes a soda bottle and then opens it quickly, which the soda explodes

Aizawa: This is what your blood does if you don’t take your time getting to the surface. You could get paralyzed and we would have to end the entire event. If you take your time to get up, and use your pony tanks if you really need it, then you won’t get bent. Now everyone, you guys can go in.

Denki: Sweet!

Everyone started having fun underwater, while Aizawa and Vlad watch the lil gremlins