There is a vertical-axis variant of the Banki-Michell crossflow turbine that might be appropriate. (I understand that these have been used as tide motors, too.)
I'd be a bit dubious about putting a turbine under a marina pier, though. Falling off a boat during heavy tidal flow can result in someone being dragged under the pier. That's troublesome enough if there's nothing under there but cabling, sea life, debris, and such. But if there's a turbine down there they might get sucked in and chopped up - or stuck to the intake by water pressure and not able to get free and back up to breathing air (as sometimes happens to people who get too close to a single intake in a swimming pool or hot tub).
So I'd recommend that any such turbine be located where moored boats - especially the sides of the boats where people going on, off, or slipping off, would heat the water - aren't upstream of ithem under any part of the tidal cycle.
As an alternative, consider mounting such a turbine on floats (turning it into a barge) and mooring it to the end of the pier or in an unused mooring (with the opposite mooring, if any, also vacant.)