There is a breakable wall near one of the water spawn areas. If you break that, there will be a red cube, you must dip the red cube into 3 of the water squares in a correct order, it will play a sound "hooha" when u dip it in the correct one. Once that sound plays after 3 consecutive water dips with the cube, another door will slowly, and painfully take its sweet time opening. Once it does, you will take the red cube, and place it into the portal in the room that has opened. You will then find yourself in a sort of flesh tunnel system. In there, you're gonna have to find a yellow cube, once you find the yellow cube, there will be a white portal next to a big water puddle. You will put the yellow cube in there and follow along with it.

You will now be taken back to the spawn. Find the yellow cube at one of the 3 spawns, then take it to the original room that had the breakable wall, there will be a new portal that has appeared, Put the yellow cube in the portal and go in it yourself. There's now a green cube, take it through the portal and follow along. Again, you will be sent back to the spawn, now find the green cube at one of the 3 spawn locations, and take it back to the same room. There will now be a new portal, take the green cube into that portal, and go in it. You're now in a walled off room with no doors.

There is a secret passage in one of the walls, just hug the walls and walk around until you slide in. Once you find it, there's a giant coin on the wall (you can hit it for a little noise or something, not sure if its necessary though.) Once in that little secret hallway, there will be another red cube, grab it, and the exit to that room is another secret door right next to the cube, take that cube into the portal in the new room. Now find that cube again at one of the three spawn locations, and take it back to the green room that transported you to the flesh tunnel. Once there with the cube you will need to find a red portal in the flesh tunnel, and you will stick the cube in there.

(Not sure if anything is supposed to happen, but it destroys the cube lmao)