The aircraft cable we use is stainless steel also. I'm sure you can get other materials. Its seems like its rated at like 15000 lbs. Prolly around 3/8 size. I'm sure someone will look up a chart but I can tell ya for sure. Its strong enough for what your doing. You stated in another thread you have rebar anchored in. I would wrap with garden hose like toy was saying and go for it. Not sure how many years it will last but I'm sure it's in the double digits.
So is the airline cable better at all... stronger, safer maybe, or lighter? Sorry for all the questions, just trying to do what makes the most sense long term and keeping things as safe as I can (guy who cleaned it out cringed at the idea of those heavy chains he found at the bottom). I did a quick search and found coated and uncoated, and one was 3/8 as you said.
They make a cable clamp that you could secure it with but in your case you might consider getting a crimping tool and crimp a clamp on, a lot less chance of getting scratched up on when in the water, also the coated stainless steel cable will last indefinitely in the water and be a lot smoother if you came in contact with it underwater. Also the breaking strength of it is pretty high, my theory is a 3/16' to 1/4" cable would anchor something in place pretty well.
All the really good ideas I've ever had came to me while I was milking a cow.