I'm playing first time on deathworld and I'm mining lots of stone to wall off big chunk of map in early game, before biters expand, but I have no way of cutting them off from water. I could place turrets but mass turrets are too expensive for me right now.
It would be useful if this mod modified avaiable placement of walls to include shores/or any water if shores only are not possible.
For now I'm using offshore pumps, but they aren't as cheap and durable as walls + I dind't had opportunity to see if it work at all at stopping them. (edit : it does not stop them and it's not guaranteed for biter to focus it, but pumps are taking some space so in some cases biters attack it)

Fix is - build landfill ~3 tiles into deep sea and place walls on it.
Yet it would be cool addition to this mod if you let building walls where you can move on foot or at least to let it build on any water. I think it would be related to this mod as it allows to move through water, so It should also give ability to stop from moving through water. On the second hand as I'm thinking now - walls on water would be more op than walls, because after being taken down enemy would still have speed debuff.. So thats good reason to not implement it.