I have an idea that I thought of while swimming against a strong current, after drifting quite a ways away from the rig and boat last weekend.

I remember as a kid how fast you could move over water on those little cheap plastic rafts. How about a BC that has a deflated raft of sufficient boyancy to hold you and your gear. You can air it up by the push of a button using the remaining air in your tank. It wouldnt have to be that big to help quite a bit.

Give me a free one if you make it.
I sure could have used it. It was a 30 minute steady tiring swim to the boat.

Check out the Halcyon Inflatable Life Raft. It folds up into a nice little pocket and is there "just in case"
Sounds kind of like what you are looking for.