モブの上に乗っているクリーパーが水の中に入ると降りてしまう問題を解決したい

  spawn zombie at {_loc}
  set {_mob} to last spawned entity

  spawn creeper at {_loc} with nbt "{NoGravity:1b}"
  set {_creeper} to last spawned entity
  set passenger of {_mob} to {_creeper}

  spawn zombie at {_loc}
  set {_mob} to last spawned entity

  spawn creeper at {_loc} with nbt "{NoGravity:1b}"
  set {_creeper} to last spawned entity
  set passenger of {_mob} to {_creeper}

  spawn zombie at {_loc}
  set {_mob} to last spawned entity

  spawn creeper at {_loc} with nbt "{NoGravity:1b}"
  set {_creeper} to last spawned entity
  set passenger of {_mob} to {_creeper}

  spawn zombie at {_loc}
  set {_mob} to last spawned entity

  spawn creeper at {_loc} with nbt "{NoGravity:1b}"
  set {_creeper} to last spawned entity
  set passenger of {_mob} to {_creeper}

function select_mob_zombie(loc: location):
    
    set {_helmet} to leather helmet
    set {_chestplate} to leather chestplate
    set {_leggings} to leather leggings
    set {_boots} to leather boots
    dye {_helmet} blue
    dye {_chestplate} blue
    dye {_leggings} blue
    dye {_boots} blue
    enchant {_boots} with depth strider 10

    spawn zombie at {_loc}
    set {_mob} to last spawned entity

    set custom name of {_mob} to "&7《&bドラウンド&7》"
    set max health of {_mob} to 20 + {game_data::drowned::zombie::health}
    set health of {_mob} to 20 + {game_data::drowned::zombie::health}
    set helmet of {_mob} to {_helmet}
    set chestplate of {_mob} to {_chestplate}
    set leggings of {_mob} to {_leggings}
    set boots of {_mob} to {_boots}
    set {_atk} to 2 + {game_data::drowned::zombie::atk}
    add "{Attributes:[{Base:%{_atk}%d,Name:""generic.attackdamage""}]}" to nbt of {_mob}

    spawn creeper at {_loc} with nbt "{NoGravity:1b}"
    set {_creeper} to last spawned entity

    set passenger of {_mob} to {_creeper}

function select_mob_zombie(loc: location):
    
    set {_helmet} to leather helmet
    set {_chestplate} to leather chestplate
    set {_leggings} to leather leggings
    set {_boots} to leather boots
    dye {_helmet} blue
    dye {_chestplate} blue
    dye {_leggings} blue
    dye {_boots} blue
    enchant {_boots} with depth strider 10

    spawn zombie at {_loc}
    set {_mob} to last spawned entity

    set custom name of {_mob} to "&7《&bドラウンド&7》"
    set max health of {_mob} to 20 + {game_data::drowned::zombie::health}
    set health of {_mob} to 20 + {game_data::drowned::zombie::health}
    set helmet of {_mob} to {_helmet}
    set chestplate of {_mob} to {_chestplate}
    set leggings of {_mob} to {_leggings}
    set boots of {_mob} to {_boots}
    set {_atk} to 2 + {game_data::drowned::zombie::atk}
    add "{Attributes:[{Base:%{_atk}%d,Name:""generic.attackdamage""}]}" to nbt of {_mob}

    spawn creeper at {_loc} with nbt "{NoGravity:1b}"
    set {_creeper} to last spawned entity

    set passenger of {_mob} to {_creeper}

command /ridingtest:
    trigger:
        set {_loc} to location of player
        spawn zombie at {_loc}
        set {_mob} to last spawned entity
        spawn creeper at {_loc} with nbt "{NoGravity:1b}"
        set {_creeper} to last spawned entity
        set name of {_creeper} to "test"
        set passenger of {_mob} to {_creeper}

on dismount:
    if event-entity is creeper:
        cancel event

command /ridingtest:
    trigger:
        set {_loc} to location of player
        spawn zombie at {_loc}
        set {_mob} to last spawned entity
        spawn creeper at {_loc} with nbt "{NoGravity:1b}"
        set {_creeper} to last spawned entity
        set name of {_creeper} to "test"
        set passenger of {_mob} to {_creeper}

on dismount:
    if event-entity is creeper:
        cancel event