I've been in a boat that launched/loaded like that, on that same beach. You go to the "fish camp" where the boat and tow vehicle are, pile into the tow vehicle, and trailer to the Boat Launch. Tow vehicle unhitches and you board the boat via a stepladder. The launching tractor is a "log skidder" and at the time they ran a two-man crew. One driving the skidder, one operating the trailer's winch. The winch has only a few feet of chain. Just enough to get a couple turns when the boat returns. Boat skipper starts the outboards dry as the skidder pushes the trailer into the surf. Winch crew disconnects the chain. Skipper backs the boat off when it's at depth. Skidder parks the trailer till called on VHF to prepare for retrieve. Boat Launch is a little village during Halibut Season. They haul in buildings on skids, concessions, etc. Day after, it's a vacant, rutted beach.
From the Alaska DNR Site:
Marine Services LLC, is a private company that provides tractor assisted boat launching services at Deep Creek beach under a permit issued by Alaska State Parks. This service allows recreational boaters and charter operators to launch boats into Cook Inlet. Cost is $65.00+tax per launch and retrieval.