The wharf is where the ships meet the town. Ships can tie up directly or to connected docks.

To keep it simple they should be made of "stone" (grey), 6 bricks high and designed to connect to adjacent wharf sections and the risers which support the building blocks of the town.

Simple wharf.

Wharf in position.

Can I build Bigger/different?

So long as the six bricks high at each end and along the back and six studs deep is met at each end of your wharf section there is no reason not to customize it.