Break the first piece of floor in the drowning room, then go back to the previous room.
Recoil slide until you fall, and keep going at least one more pixel on the minimap.
Move left. You will have to jump out of the wall.
In the next room, make a series of jumps back up almost to the surface of the water. You will have to jump right a little to trigger the rocks falling and flooding.
Jump a little out of the water to trigger the drowning animation. You have to jump enough that you descend far enough into the water to get under the overhang.
Hold left until you get into the next room.
Float upwards and head for another room. Sometimes the room to the west works, as in the video below. I found going to the boomerang room to the east worked more reliably.
You might need to hit a room transition at the right time, such as by moving back and forth between two rooms. You can use the click of the flashlight toggling between rooms as a guide.
When the save room appears, the minimap should show your destination room. Move into the boomerang room and hit left to trigger the horizontal skew.
The setup in the drowning room is important because otherwise it doesn't work.
Sometimes you don't get a destination room but you skip the respawn animation.
You will not have a valid save point active. Savewarping or dying will crash your game, and you will not be able to load it again. You must reach a save point and save there manually to fix this.
You will not have the map tile for the usual Glacier save point either.