A good friend almost had that happen. He had his 24' boat up for sale and a buyer came to see it. John said he'd take it down to the lake for a test run. He drove down to the boat ramp (downhill all the way) with the guy riding with him.
As John was backing down the ramp, he realized the boat was going faster than the truck, so he goosed it, got the boat into deep enough water and stood on the brakes. The boat slide off gently, and they went round, grabbed the lines and tied it up to the dock. He never did explain the "automatic launch system" to the guy, but he bought boat and trailer!
Frank and Eileen
No longer RVers or FR owners