Medium diving cranks down the sides of slips works. As does skipping jigs and Senkos under the walkways. I always fish them if allowed. And I also fish the shade lines around them. Usually get one or two a day from them, when they are on a lake I'm fishing. Some of my biggest bass ever and a few of the exciting catches I've had have been marinas and boat docks. Caught to smallies on a craw colored crank off a boat house. .....on one cast. Boated them both.
Basically, fish it like any other cover. Especially is the boat docks are scarce on a lake. Makes for unique cover that fish might be drawn to.