The collective noun is a bubble of scuba divers.
scuba divers
Free divers do but scuba divers do not need to. Scuba divers take their air with them and would have no need to hyperventilate.
They swim
seebees
In the Water....
scuba divers
Scuba - self contained underwater breathing apparatus
Scuba Bob's Ocean Quest - 2006 Fearless Divers Scuba Rangers 2-7 was released on: USA: 2007
Skin divers are people who dive into the ocean without using special equipment, unlike Scuba divers.
They don't necessarily have to be, I think.
Slowly