they need to know how long they can be underwater, and how deep they can go with the air in the tank.
Free divers do but scuba divers do not need to. Scuba divers take their air with them and would have no need to hyperventilate.
Technical scuba divers do, but recreational divers do not.
Like all adults or older teenagers; scuba divers need English and Maths also physics and scuba diving training. Hope I answered your question xx
The collective noun is a bubble of scuba divers.
Scuba divers.
dive
scuba divers
Many people use a SCUBA suit for diving. Sport divers, police divers and some Navy recovery divers.
They swim
seebees
SCUBA
they don't