Is there a way to increase your oxygen capacity further?

[poke_ravi]

So far I've gotten the oxygen tank which caps the O2 at 75. However this still makes it pretty much impossible to explore the sea floor or any deep caves. Is there a way to further increase your oxygen capacity?

[tran_fors]

Yeah, in addition to the tank "slot" on the right-hand side, if you carry more tanks you'll have more air capacity. Supposedly, if you carry more tanks you move slower though - I wouldn't know, I only carry one additional tank. (speed is more important than O2 capacity, IMO)

Also, when you find the Modification Station, you'll be able to apply one of two air tank upgrades to each tank. (capacity, or slows-you-down-less)

[Twilight]

2 big tanks give you sth. like 225(?) oxygen

[Lord Of Dorkness]

You can also build 'pit-stops.' A single corridor/room with a power-source and an air-lock. Bit work intensive since you need raw-materials, but very useful for stuff like, say, the caves to get deeper then your current tech technically allows.

How I got most of my lithium on my first play-through, actually. At least before I found all the gear for the mini-sub.

[Cougarific]

In my experience ^pit stops are far more efficient than air pipes but since nobody has mentioned them yet I'll just throw them out there as an option. Air pipelines from the surface are slow and finicky to build, cumbersome (take up a lot of inventory space during the building process) and not very flexible - but for all that, they do exist.

[Dala]

Or make an air bladder for a quicker way to surface, very useful early game.

[Halifax789]

or even 3 or 4 tanks if you are pure exploring and not gathering

[Iskandar]

3 tanks+rebreather+Seaglide and I can somewhat explore down to 200 meters or so, maybe a tad deeper. It does need to be day, though, as there is no spare time to fumble around in the dark.

[Geno Five-Two Chiliad]

The more tanks you have the longer you can stay down, but you also swim much slower. You get bit by animals more often and you drown more often as you are so slow in getting to the surface.

The best way to explore deep -until you get a vehicle- is with a seaglide + extra tanks and bunch of batteries. The extra weight will not slow the seaglide down at all. The trade off is a much smaller inventory as you not only have to lug the seaglide around, but also space for battery packs to power the thing.