The Diving Tank, when equipped, allows a player to breathe underwater until it runs out of oxygen. The amount of oxygen left is indicated on the icon of the Diving Tank. It has a maximum of 600 seconds worth of oxygen.
Similarly to the Jackhammer, once all the "durability" of the Diving Tank is gone, it can be refilled at a workbench.
The Diving Tank can only be found in crates. They can't be researched as they don't have a blueprint, and as such, can't be crafted.
There are no skins for the Diving Tank as of April 15th, 2020.