One of the hardest physical things I've ever done was to step off a pilot boat onto a ladder in 8 foot swells. The boat couldn't hold position, and was rising and falling 8-16 feet constantly, so I had to time my step damned near perfectly in 3 dimensions or wind up in the drink, possibly crushed. I managed that, then had to climb up 36 feet of rolling freeboard -- go ahead, laugh, think that 36 feet isn't shit. Then go try it on a rolling supertanker (roll one way, press against the ship, roll the other, and you're dangling) and get back to me. Anyway, sure could have used something like this that day. Thought I'd seen it all, but I'd never seen this method.