Ultra High Capacity Tank (Subnautica)

The High Capacity Tank is a piece of equipment and an upgrade to the regular tank. It is crafted by using the workbench.

It boosts the player's oxygen supply by 60 seconds. This is twice as much as a regular tank.

The player can carry multiple tanks at a time to further increase their oxygen capacity up to (but lowering space for other things). The High Capacity Tank also take up four slots in the player's inventory.

The player can carry maximum of 12 High Capacity Tanks if the inventory is cleared first. This will boost the player's oxygen supply by 720 seconds (12 min).

While each High Capacity Tank adds to oxygen, it also adds to the player's current weight, therefore decreasing the player's swimming speed. (As of update B55, the High Capacity Tank does not affect player speed.)