When you go scuba diving, they include extra cylinders for emergency breathing.
That's important. There is surprisingly a great deal of safety knowledge required to scuba safely, such as rising slowly instead of too quickly.
True, and for ambient pressure diving, you are exposed to all of the pressure of the water.
You mean without a scuba suit? I haven't heard of that before. Is it newer?
Yes, without a suit, though humans are not well adapted to the conditions of diving, so equipment is recommended.
Are you familiar with the depth limits of ambient pressure diving?
No I am not, but I do know that underwater areas can imposer psychological and physical stress on all divers.