Helium mixed with oxygen in a diver’s tank creates a mixture called Heliox, which was a milestone discovery in WW2 that helped divers swim further into the depths and is still used to this day.
There’s a variety of cool nifty things I imagine the Subnautica 2 team could come up with. Helium tanks/silos at a base to store it. Different tools to help swimming.
A helium grenade, for example. Non-lethal item that you throw at creatures so they float up and away until the bubble breaks lol