Zombies should not be expert deep sea divers

Describe the bug

I am on a secluded island in my debug world (which has hordes enabled) and roaming zombies continue to emerge from the lake.

Steps to reproduce

1. Create a world with hordes enabled.
2. Find a lake with an island you can teleport on.
3. Wait for stuff (in this case, I had to wait 105 ingame hours until the moonshine was fermented).
4. See zombies emerging from the lake, especially if a city is nearby.

(Yes, the island right next to the shore should not exist, this is wacky mapgen)

Expected behavior

Zombies should not wander through hundreds of tiles of deep water. I get that they can wade through moats but this is too much in my opinion.

Screenshots

No response

Versions and configuration

• experimental

Additional context

No response