What happens, God forbid, if you come up out of air and had no air in your BC. First thing you need to be able to do is SWIM to the surface. A BC is not supposed to be used to lift you to the surface. It is a buoyancy COMPENSATING device, not an elevator device. So once on the surface, with the empty BC, you will need to tread water(swim) while trying to manually inflate the BC. Then guess what????? You will need to SWIM to shore or the boat.
Anyway, I am sure you get my point. Learn to swim then get your certification. I sure would want my buddy to be able to swim.
If you are have no air in your BCD then you are a fool for dumping all the air in your BCD in an OOA situation. In this case, you would have to orally inflate at depth, or if you were in a CESA situation, you would have to do an EBA because there is no way you could do a CESA from depth against significantly negative buoyancy.
You KICK to the surface, not swim.
You KICK at the surface while you inflate your BCD, and if you are too exhausted to inflate your BCD while KICKing, you drop your weights to get buoyancy. Keep in mind, if you are properly weighted, you will be neutral or slightly buoyant (due to the completely empty tank) at the surface.
Then you put your snorkel in your mouth (pulled of my BCD pocket in my case), and KICK to your exit point, the same as you would have done if you still had air left in your tank.
Don't get me wrong, I think that everyone who is around water should have basic swimming skills, but, when you are in full gear, you don't swim because you can't swim in full gear. This is why we wear fins. If you don't believe me, try diving without them sometime.
On another note, my kicking technique has improved substantially since I started diving. It used to be if I was being chased by a crippled shark while swimming, I was going to die. Now I might stand a chance.
As a side note, here is the Canadian Swim to Survive standard:
- ROLL into deep water
- TREAD water for one minute
- SWIM 50 metres
It is extremely minimal, and is prescribed as the minimum skill set required to survive if you accidentally fall into deep water. I you don't have these bare bones skills, you should not be scuba diving or doing any other recreational activity that brings you near the water.