"OP asked for an automatic not an in-motion. The SK-3005 is automatic and Direct TV HD. He is concerned about elevation change from water level. "
To use on a boat, it is implied it would have to be in-motion. He didn't mention "boat" in his initial post which was a pretty significant variable.
Not sure why OP can't just put a Slimline on the bank or the dock and run the cable. That's the way I see it done in most marinas. Even if the dock floats, maybe there are stationary pilings. That doesn't work, he could do a pretty long run to the bank via RG-8.
