Scuba Tank

The Scuba Tank is an item that allows players to breathe underwater, and store up to 40 minutes of the Water Breathing effect.

When underwater, the Scuba Tank grants you Water Breathing while it still has Oxygen remaining. It does not consume Oxygen if the player is already under Water Breathing effects (such as a potion or the Turtle Shell), but overrides any other Water Breathing effects when activated. It also has the Aqua Affinity enchantment, which is normally reserved for helmets, allowing the player to mine effectively underwater. Overall, it is a more inventory-efficient and convenient way to use Water Breathing potions fit for long exploration and underwater immersion, at the cost of protection.

While holding the Scuba Tank in your main hand or wearing it underwater, an Oxygen meter will be visible displaying your remaining Oxygen percentage. The color of the display changes based on the remaining oxygen.

This item is currently unobtainable, but I'll take suggestions for a crafting recipe or method of obtaining it here.

Refilling

Scuba Tanks can be refilled by throwing it on the ground, and then throwing Potions of Water Breathing at the item. These will consume the Potions and refill Oxygen equal to the potion's duration (3 minutes for regular, 8 minutes for long). However, it still caps at 40 minutes of Oxygen. Picking up the Scuba Tank transfers the Oxygen to that player.

Oxygen is actually stored per player, not per item, meaning that the Scuba Tank's Oxygen cannot be transferred between players and all Scuba Tanks share the same Oxygen for a single player. This may be changed in the future.