What Walter said.
Basically, the diver is confined to the surface by their panic, and that is the great equalizer. Their weights are below the surface. Their inflator is at least reachable from below the surface. Their tank is below the surface. Pretty much, everything you need to interact with is where they don't want to be.
(Anyway, frankly, I wouldn't even go up against a five-foot 100-pound lady on the surface, so the fact I wouldn't want to go against a defensive lineman on the surface isn't really saying much.
)
If you're just getting the diver buoyant (which is generally sufficient to break the panic cycle), you just dart in underwater, do it, and swim away underwater. If, on the other hand, they're buoyant and still stuck in panic mode, it's still not a fair match. You can simply latch onto their back (tanks, valves, and the like are great for holding onto for the ride) and work from there.
The simple fact of anatomy is that it's *really* hard for a diver in panic to reach behind their back and get you. Think about it. Can you undo your BC's cam bands while you're wearing your BC? *That's* where a rescue diver will be hanging on. Even if they can touch you, they have no leverage; as long as you're riding them, you're "safe". When you've got them by the tank, there's not much they can do but flail or give up.
The basic concept of rescue diver training is to
know how to "cheat". You never go up against a diver in panic in a fair fight -- they'll win. You reach for them or throw things to them from positions where they can't get you. You swim toward them wielding floats. You go underwater where they *can't* go. You get behind them where they can't reach you. Panic is a powerful thing, so you use every advantage you have to make mismatches and come out on the winning side.
Once during a rescue class I had an assistant who weighed about 280 and since the divers in the class were all pretty competent divers I told him to be a little aggressive when they attempted a rescue. Two guys did very poorly and he drug them under, the tiny woman yelled for him to inflate, then to ditch his weights, she then dropped below and went behind him, he was bucking like a bull and she looked like a rag blowing in the breeze but she held onto his first stage and ditched his weights for him, never once did she look in danger, wish I had a video of it.
I've seen similar several times in my much shorter span, but alas, I too have never captured it on video. (If J.'s little sister ever takes Rescue, I'm calling the big DM to come to the pool for training, and I *will* get video. $10 on her. :biggrin
