I'm making a map involving islands. I don't want the terrain to repeat, because the build I'm planning takes up one group of islands and I don't want mysterious uncharted islands to be visible on the horizon, especially as part of the build will involve flying and it will be easy to see those areas. However, when I choose not to repeat the terrain, I run into a few problems.
The terrain cuts off at the edge and makes a visible line in the water. I'd like to know if there's a way for the terrain to continue looping but for it to be flat beyond this area.

Also, outside that area, the water seems to act as though the terrain is still being looped, causing a shadowy outline and visually missing area in the middle of where the island would be.

When I set the water to not repeat, the second problem is eliminated but a new one is introduced. It creates this unpleasant change in color at the edge of the map (not to mention the edge of the terrain is still clearly visible)

When I also disable UseDepthMask, the third problem is also taken care of but the first one is even more noticeable than before, and the water becomes very bright and mirror-like, and seems to be missing its texture.

I really need to find a way to get past these without reinstating looping terrain. Any help would be appreciated.