Agree, on SCUBA as an emergency device--and that is why I recommended it. I had a material similar to blue tarp but thicker (used to catch olives in the med) foul the prop. Another time had a large plastic sheet fould the prop. A lobster pot entangled (cleared with out SCUBA). There are hunks of floating lines. Also long line fishing grear and nets which have been cut loose. Some can be cleared with a knife and a simple dive. But when poly prop line has fused on a shaft--it can be hard to untangle--and a hack saw may be necessary. Also going over the side in a seaway is not easy--your boyancy is different than that of the boat and you will be thrashed around. When you are not under way, there may not be stabalization and motion may increase. I tended to wear a wet suit (or two light wet suits)--and no weight belt--to keep me up against the hull when working under water. Pretty much one hand on the running gear and the other doing the work. The point is well made that Scott's vital capacity (that which is available for oxygen exchange is half or less of "normal"--and he will not have the reserve that those of us with two lungs will have. Bob Austin