When smaller spawner biters spawn (looks like it) smaller biters, they're able to walk on water. For example, they attack on the edge of a lake. This allows them to walk across the lake and my walls. This is not enemies spawning landfill to prevent water ditches. Spawner enemies are walking on water, which should not be allowed.

Tiny spawns do not have a collision zone and can pass through walls and sometimes move through water if the target is in line of sight. This is exactly how it was intended.

Also, with your mod set, shallow water is a passable tile. Any biters can move there - both land and sea

Pretty sure shallow water only goes roughly 6 tiles from shore, not 15+, but I digress.

Here's a picture proving that spawned biters can walk on any water tile type: https://ufile.io/zhlejcq3