123

Requires:

"h_navigateUnderwater",
{"or": [
  "h_useSpringBall",
  "canMidAirMorph",
  {"and": [
    "Gravity",
    "canBombHorizontally"
  ]},
  {"and": [
    "Gravity",
    "canLongIBJ",
    "canJumpIntoIBJ"
  ]},
  {"and": [
    "Gravity",
    "canTrivialMidAirMorph",
    {"or": [
      "SpaceJump",
      "canUseFrozenEnemies"
    ]}
  ]},
  {"and": [
    "canTrivialMidAirMorph",
    "canDisableEquipment"
  ]}
]}

Dev note: It's possible to get in without a mid-air morph by rolling off from above, but that requires disabling Gravity and/or crab hits and the crab not killed. That's a lot of work to avoid something simple and barely reasonable at that level anyways.