I've maxed out all my stats except lung capacity, mainly because I never found much use for it. But last night, while playing "A Boat In The Bay" with a crew I found a pretty cool use. We were all flying in a Buzzard to the location when one of the guys with maxed out lungs said "I'm gonna try to swim underwater to it, you guys provide air support" and promptly dove in the water. He swam underwater for quite a ways and got to the boat without having to come up for air once. None of the NPCs even realized he was there until he took off in the boat.
Now that I have a reason to care about lung capacity, do you guys have any other uses for it that you can share? Any motivation for stuff I can try once I get it is appreciated!