Need Advice: Moving a Hydrohoist

A friend of mine has rented a slip for the summer. He's going to look at a 10,000lb hydrohoist today. It's at a marina pretty far from where his slip will be. He wants to buy it, tow it to the boat ramp that's about half a mile from where the hoist is now, load it on a trailer, drop it at the marina where his slip is, and hook it up. He needs advice on how to move/tow the hoist safely to the boat ramp. Basically, he does not want to unhook it and have it sink to the bottom of the lake. Has anyone done this? I'm out of my element here.