I have an idea but it wont let me suggest it .....

[PercyBanana]

what if there was like a auto build enclosure coz i cant figure out how to make an underwater habitat im a noob so i taught it would be a good idea then you can add details for what ever animal you want in it just a thought :)

[Nariel]

What seems to be the issue? Digging out the terrain? Underwater feeder height? Underwater viewing?

There are many tutorial videos online, if you could narrow down your issue a little bit I'll gladly suggest some videos that can help you :D

[Jaggid Edje]

You can use blueprints to achieve this, though you cannot customize the size or anything...just plop them down. If you have the aquatic pack, there's already a few such blueprints available in the DLC. And you can download more from the workshop.

[Firestar]

What exactly is the Problem? Is it about diving or Penguin or Seal Happiness? If so, the Water needs to be at least 4m deep. Even a few Centimeters less make the Animals unhappy and unable to dive (hope they will find a Way to fix this and remove the Deep Water Need from the Giant Otter). I would reccommend what I'm always doing when I'm building this kind of Enclosure. Test the Depth with a 4m Piece of Wall and make sure that it is completely covered by Water. Then everything should be fine. The Underwater Feeder needs slightly deeper Water but for that you don't really need to change the Terrain, you can also just push it into the Ground until it fits after you've already added Water. Also think about using the new Water Customisation Options to make the Water clearer if you want to add a Underwater Viewing Area

[Just Kevin]

You can edit blueprints.

What you mean are not actually underwater habitats, they are habitats with water in them.
If you mean habitats for creatures like grey seals, they still need a fair bit of land, but very deep water as well. What I do now is create a large land platform using the landstamp at max. Then use the other landscaping tools to sculpture suitable slopes in to it so the animals can get in and out of the water once you put it in. Next, away from the land platform, I raise a glass barrier at normal ground level, with a top higher than the land platform and up on to the land platform to complete the barrier. You can adjust the height of the fence on the land.
Make sure there's space at one end of the fence on the land platform to place a gate and a bit of path, with steps leading up to it from a keeper hut.
Fill the lower part with water.
Lay a path around the glass so guests can see in.
It just takes practice.

[Just Kevin]

Oh, when you click on the barrier, it should tell you the depth of water. If not then click on a creature in the habitat and it will tell you if the land size is enough and the water amount (it works on volume) and its depth, and if that is also enough.