The Dream Beach (夢海岸, Yume Kaigan, Dream Coast) is an area accessible from the School through a hole in the wall of one of the classrooms, a tunnel in the lower section of the Highway, and the underwater maze in Jigsaw Puzzle World.
By entering the hole in the classroom's wall, you have to crawl through a small pipe. At the other end of the pipe is a small area on the ocean floor (沼の底, Numa no soko, Bottom of the Swamp). Huyure-chan can be found here, along with a fishing hook dangling in the water. Interacting with the hook will take you up to the Dream Beach.
If you interact with the hook using the penguin effect, Urotsuki will be caught and end up inside of the kid's fishing bucket with a very sad looking fish, which will flatten itself if you interact with it. On the right side of the bucket there is a valve that Urotsuki can open. If you interact with it, Urotsuki will be washed out of the bucket in a stream of water next to the kid fishing, and fall back into the ocean.
The Dream Beach itself resembles a sandy beach covered in palm trees, with a short concrete pier and a beach house nestled in the trees near the shore.
Out on the pier a kid in a red cap can be found fishing near a single lamppost. Interacting with the side of the pier while standing beside the fisherman will let you return to the underwater map, and if you interact with the lamppost a ghostly woman wearing a tattered red dress will appear under it.
Inside the beach house a girl in a white dress and an old woman can be found sleeping next to a large pot. If you equip the child effect near the girl she will run out of the house and continue running down to the end of the beach, until she disappears with a laugh.
If you head along the shoreline to the east you will eventually reach a different section of the beach, which is littered with the skeletons of various large sea creatures. On the far east side of the area there is a large fortification of tank traps along the shore, along with a road that runs along the bottom of the area which eventually leads into a large overgrown tunnel that will take you to the Highway.