Firstly, thank you for this mod! It always goes into my modpacks whenever Island Start is involved!

Here's a few nice-to-have suggestions to make it even better. Whaddaya think?
1. Mask character sprite to half height when "swimming". So when a player decides to jump into water, would be nice to see it reflected in the sprite as well so they're not just walking on water like Jesus.
2. Same as above for biters also if possible since they can also swim.
3. Would be nice to support alternate character sprites (minime support) and alternate biters support. Maybe a runtime script to make swimming sprites in memory?
4. Disallow vehicles, spidertrons in water. Not sure if this is feasible but if we can disallow entities by mask, would be nice to only have boats, cargo ships etc. in the water. Could be a mod setting with a default.

1. Yeah this would be nice but I steered away from this and am thus also not planning on adding this due to performance reasons. I do believe it is technically possible to cut most character sprites in half and have a somewhat decent emulation of being in water but even this requires per sprite adjustments. My main concern with doing something like this is it will double the memory requirements of any character sprite (which is already a fairly large set of sprites (all animations in all possible orientations see the folder Factorio\data\base\graphics\entity\character)). The amount of work is beyond what I intend to spend on this mod.

2. Same as the answer for 1 it is too much work for what I intend to spend on this mod see also `Factorio\data\base\graphics\entity\biter Not only are these sprites multi-layer they are also multi color and have shadow sprites. Shadow sprites in water especially with bodies under the water (or cut off) you'd have to rebuild the shadows completely. Not a trivial task.

3. Same as 1 and 2.

4. I'm not sure this is possible yet since all of the mentioned things fall under the player-layer collision mask which is what I removed from all water tiles to make swimming work. That or the approach has to be completely different and will impact performance greatly. Currently this mod has almost no performance impact at all.

So unfortunately I have to reject all of the good ideas at this time.

Ah, that's understandable. Thank you so much for the detailed response! And thanks again for a great mod!