Yes, scuba diving involves being completely untethered from the surface air supply. Have you ever been scuba diving?
Of course yes. It could be called  a science when the diver uses a self-contained underwater breathing apparatus
Scuba Diving is an interesting thing.  There's a lot of ocean science involved.
Scuba diving is a form of underwater diving where the diver uses a self-contained underwater breathing apparatus (scuba) which is completely independent of surface supply, to breathe underwater.