Better tools for making smooth underwater Terrain

As a Roblox developer, it is currently too hard to build reefs and islands. I can’t really compare the behavior above ground versus under water. But in my specific use case, I’ve generated a large plane of ocean. And I’ve used a FillRegion to place a landmass underwater from the floor to a bit lower than the water’s surface. I then draw on top of it until I get a small landmass in the middle of the ocean. But connecting the sides of this square to the ocean floor in a smooth slope… is near impossible under water. Because I can neither ignore water or smooth the sand.

In the picture below I tried using a fill region on a block rotated at an angle. Which gave me more desirable results and would be perfect if I could smooth it.

But sadly I cannot.

If Roblox fixed this issue, I would be able to create vast underwater biomes amongst other types of biomes out of smooth terrain that is ready for other props and assets to further improve the aesthetic, dynamic, and immersion of not only my game, but countless others as well.

I recommend investing some research into a waypoint styled system. I guess it would probably do best for me to mention a flatten tool (that doesn’t exist) here as well. If both of these tools used a waypoint system that is selecting more than one point on a map, and hypothetically drawing a line between them. And flattening based on the height of the two points (or more) you could end up with a much more flush environment using smooth terrain. Maybe you could retain the old brush behavior by default but switch to a path based solution by holding [Ctrl].

The regular brush approach…

What can I say… it leaves much to be desired.


I’m pretty sure there have been some massive underwater biomes created before. If my memory serves me correctly, @Beeism has taken a crack at it as well as @ColonelGraff.

Would be interesting to hear from anyone who does underwater terrain stuff.

It’s just insanely difficult without using different types of methods, or scripting a tool of your own. Not impossible though. I’m gonna continue creating my underwater biomes regardless of this feature request. It’s just that this feature request compliments and speeds up the process.

If anyone would like to share methods or ways to make this easier in the meantime, We can do so in a Private Message, or some more appropriate category for a discussion. I just really don’t want to take this off topic ya know. But more use cases here would be much better, so if you support this request and have something to add please do so. It might increase the priority here and who knows by the time we turn 60 we’ll be using Flatten and Smooth tools in studio. :rofl:

That’s exactly why I tagged those two individuals. Would love to hear how they work with it.


There’s really no easy way to do it, especially since the smooth tool is broken underwater (it hardly even smooths terrain above ground.) Another annoying issue is that when filling a section with water it roughs up the terrain beneath it making it look all blocky.

This is why we need better terrain tools, it’s currently very difficult to create large areas of polished looking terrain with these tools (I’m pretty sure you’d have an easier time making smooth terrain in Planet Coaster.) They’re very undercooked, and I haven’t found many plugins to speed up the process aside from Quenty’s Part to Terrain, which can only do so much.


if you want to do underwater stuff, it’s best to have your body of water established first and then modify it afterwards. The problem is as you said tho. Most tools don’t work underwater. However there was a road map entry saying more advanced tools. So I can only hope a staff member sees this post and it gets discussed internally and somehow become a part of that.

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That’s true, I found that out the hard way the first time I tried making underwater terrain and it was a bad time.

Another issue: it’s hard to examine your underwater terrain at a distance since you can’t see through water in studio, making it even more challenging.

I simply set the transparency of my water to 1. Then you can see clearly. As in the photo above. That image is actually under water. I actually like the fact that there’s still fog because I can get a good idea of how my underwater biome looks in comparison to something like Subnautica for instance. The above image.

I’m actually okay with. The problem is just the slopes on the sand for me. Wish it was smoother.

I was referring to the surface of the water. If you want to get a good view of everything you’ve done, you can’t zoom out of the water and look at it all from a distance because the surface of the water blocks it.

Regarding underwater fog, it would be nice to at least have more transparency options to tune it and even be able to turn it off completely.