[rodguy911]

Here in the Keys diving is second only to fishing.

We have two basic divers.

Snorkelers and scuba.

Snorkelers normally stay on the surface and are usually equipped with dive masks, snorkels(for breathing only on the surface) and masks.

Scuba or underwater breathing apparatus' usually have masks,fins snorkels and tanks. The tanks, filled with compressed air, have devices,regulators, that extend from the compressed air tank to the mouthpiece and generally you have from 30-60 minutes of air with which you can safely dive under the water at various depths.

Accessories are endless. Knives, dive watches, depth meters,wet suits,go pros, its endless what you can tack on to either a scuba diver or snorkeler.

If you see someone under the water most likely he/she is equipped with at least the basics of a tank, regulator, mask, snorkel and fins. It's likely he has a bunch of accessories as well.

[Travis McGee]

For sport divers, you are correct. But frogmen don't use open-circuit scuba bottles. They use a neutrally buoyant rebreather (no bubbles) which is usually worn on the chest, not the back. 90% of the world's frogmen use a Draeger or a copy of a Draeger like this.