Standing on the platform in the room below, crouch jump up and press right against the door frame through the transition.

Entrance condition:

"comeInWithPlatformBelow": {
  "minHeight": 10,
  "maxHeight": 10,
  "maxLeftPosition": 1,
  "minRightPosition": 2
},
"comesThroughToilet": "no"

Requires:

"canCrossRoomJumpIntoWater",
"HiJump",
"canCrouchJump"

Dev note: This strat only works for platforms that are 10 tiles below the door transition (Crocomire's Room). It could be done for a platform 9 tiles below the door transition, but this would require a momentum-conserving turn-around; it is easier to just do a standing jump or spin jump in that case instead of crouch jumping.