If you mean "jetty" then that would require more things than just 3D structures: Seaplanes and water you can land on.
The water in the game is seemingly just paint/special effects so you can technically land on it-If there was a seaplane added, the devs would have to actually make realistic water by doing whatever they need to do (Make the water like a very low-hanging, blue cloud?).
Then, they'd have to make some seaplanes, which isn't on the current agenda from what I see.
Would be terrific, but I'd hold my breath.