I try to avoid building right on the shore anymore. I came up with ways to put walls etc to mostly prevent them from going around but it was more work than worth the trouble.

That said, in my current play-through I found that building along a creek/ river with a close shore on the other side, caused the event swarms to approach from across the river. So far they have been easy to shoot and one troll event only had one troll show up. Lit him up with fire and he just walked away.

Dug a moat around the hillside and planted some trees to act as troll blockers on one side, but the actual shoreline along the dock and buildings has no "defense" at all. Before I put the trees up though I would get a troll in that one side pretty regularly. They seemed to spawn often on the hillside right where I put the base.