I have seemed to have resolved the issue but loading the game on minimum graphics settings. the interface is now working again. I'm using a Nvidia 670 GTX. If I now quit and go back to using recommended settings then the interface stops working agai…
just to be clear the oxygen is just showing 45/45 but not going down when under water....I do get the sound warning when there is just 10 seconds of air left however.
Also I have 2 tanks in my inventory so it should display 105 air.