Dock/boathouse defensive building vs. mid-game events

How do you protect the against-the-water edge of your boat docks/boathouses or whatever from event-based land attacks?

Picture a base and dock near big water. Obviously you have to have access to water deep enough to launch your ships. You can't just wall-in the whole area, so it won't be completely protected on all sides. Yet with that opening to the water, since many of the mobs can swim (indefinitely, unlike the player), they will eventually path to the opening, and then to the ships and base.

The best thing I've come up with is in the shape of a big U. Water leading to the ocean stretches across the top of the U. The base is in the bottom of the U, and the dock is just above that. I use the hoe to raise the terrain at the top of both sides of the U, topped with stake walls and extending out into the deeper water, and then I add sharp stakes around all the top-of-U edges. The land-based part of the U is fine, I've learned how to build stone walls, moats, and raised terrain. But the mobs still swim around anything I build.

I'm not so worried about the flyers as of yet (assume this is prior to defeating Bonemass; roofed docks would work okay there, I'd think), but for now I'd like build something that will allow me to be able to come/go from my dock, and step off the ship into my base, etc., without worrying about the swamp event and troll event.

I'm a *certified* (in every meaning) "Wannabe Perfectionist" (i.e., I ceaselessly attempt to perfect everything... but perfect typically becomes the enemy and I overanalyze everything, building and rebuilding, etc., and that's how you end up with 1,300 hours without even coming close to finishing the game lol).

Thanks for any help or suggestions!

P.S. Quick question: if the mobs cannot see the boats (because of raised terrain), will they not path to it? Is the mob's line-of-sight something I'm not considering in this scenario?