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.