The key to launching a boat alone is a good boat ramp that isn't too shallow (drops off nicely so you don't have to back the vehicle into the water up to the rear axle) and a looooooong launch rope. Hook the rope to the tongue of the trailer before backing in, then back the boat into the water until the boat floats off the trailer, then pull the car up the ramp and out of the water so you can get out and stay dry, put the car in park, get out, grab the end of the rope that you attached to the trailer tongue, and walk with it down the dock. Unless there is a heavy wind or fast moving tide, this method is sufficient for most trailerable boats regardless of size. I've done it more than 1000 times. Extra credit: determine wind direction before backing down the launch and back down along the upwind side so the dock is upwind of the boat/car/trailer. When the boat comes off the trailer, the wind will try to carry it downwind, away from the dock, preventing unnecessary damage to the boat by banging into the dock. Again, make sure the rope is loooooong enough to do this.