They must let the boat dry out regularly. With big tides, you can let the boat go high and dry with shear legs to keep it upright. Need a way to get on and off the boat when the deck
is seven or eight feet above you. Only reason I can see for such a long and elaborate board ladder. Looks like this owner has built himself a completely self sufficient boat, screw the boatyard costs.
I do like Alan Buchanon designs.