I think it might be complicated to program, but what if you could “Teach” your villagers to stay away from certain place (e.g. Lagoon) by dragging them away from that place.
If the same villagers happen to go to Lagoon again, repeat.
Villagers will “Know” that s/he can’t go to Lagoon, so they stay away from it, until you dropped that villager on Lagoon