Bonus points to anyone who recognizes the inspiration for this room.
The water level of this room is the bottom layer of the foam core paper. Spray, painting the entire terrain piece resulted in significant warping of this paper. This was not unexpected - part of the reason for the island in the middle is to maintain some integrity in the room, and I was careful to weight down the piece with a heavy textbook while it dried to ensure that the outer edge of the room would lay flat during use. The remaining warping in the water level looks a bit like waves and is obscured by the paint job. A terrain piece with a hard floor - either wooden or stone - would need to be heavily reinforced prior to painting.