Short Version: What determines lung capacity upgrades in GTA: San Andreas?
In Grand Theft Auto: San Andreas, I'm up to a mission where you need a certain amount of 'swimming skill' in order to start it:
The mission is for the Triads in San Fierro: Woozie wants you to infiltrate a container ship out to sea.
What this means is that I need to gain Lung Capacity.
Unfortunately I haven't unlocked all areas of the map yet, so I can't:
collect all the oysters and unlock 100% Lung capacity from doing so.
So I thought I'd just rig my controller to swim in circles and walk away, and come back in an hour or so, because I thought it was based on distance swam.
However someone mentioned to me that I might actually need to swim underwater and let my oxygen drain out, then rise to the surface to get it back, in order to level up my lung capacity (which sort of makes sense - holding your breath for longer and whatnot).
Now I've tried both for a bit, and although I got lung capacity from going underwater after a while, this could also be because I'd just passed a threshold of "meters swam", and only proves that I could've been too impatient with swimming on the surface.
So, do I gain Lung Capacity simply from swimming, or by going underwater?