Gain run speed to the right and jump through the door without bonking the door frame. After the transition, continue holding right while remaining in spin jump. This strat could also be performed without passing through the Toilet, but a precise down-grab would be needed to get onto the ledge at the end; in this case it would be easier to perform a standing jump instead.

Entrance condition:

{
  "comeInWithPlatformBelow": {
    "minHeight": 6,
    "maxHeight": 6,
    "maxLeftPosition": -2.5,
    "minRightPosition": -0.5
  },
  "comesThroughToilet": "yes"
}

Requires:

"canCrossRoomJumpIntoWater"
"canTrickyJump"

Dev note: This strat only works for platforms that are 6 tiles below the door transition (which is the closest distance that occurs in the vanilla game).