If you lose the Fishbowl helmet, Murphy will give you a new one if you choose the diving option when talking to him. This helmet can be stored in the armour case of a player-owned house along with the diving apparatus.
Until the removal of Random events in 2012, if players got a random event underwater, the NPC would be wearing a Diving apparatus and a Fishbowl helmet, just like the player.
Even though the player model doesn't have a mouth hole, the chatbox head does.
Despite being members objects, the helmet and diving apparatus can be brought to Wizard Myrtle in free to play servers as a feasible diving method. It will remain on the player even after surfacing, effectively allowing free players to put on a piece of a members equipment.