Today on Midway, I was a american submarine, and I entered a battle between two Battleships, one of ours, one of theirs. Both of the battleships were heavily damaged, and the american one was starting to sink, I was able to deal the death blow to the japanese ship with a torpedo, but there were calls for "I NEED PICK UP!" everywhere, so I decided to submerge to see if there were any other enemies around, and the people started climbing on to my sub (americans climbed up, i mean). I didn't want to go underwater and leave them floating, so I started towards our nearest vessel, a Aircraft carrier, when all the sudden the Japanese sub submerges for repairs, a sniper on board my sub picks off the engineer repairing the Japanese sub, and we got on our way again (after I sank it with torps, of course). Soon we were at the aircraft carrier, the 4 to 5 people on me said thanks. And they climbed aboard the carrier. Strangely enough, later in the game I had Japanese dudes start to crawl on my ship after I submerged to look around..... I just decided to go on down.... and they drowned.
I've carried teammates on subs before too, a good way to pick up sunken victims when the landing crafts are too far for them to swim to. Not many people like playing naval battles in BF1942 since they can get boring, the subs can be really fun if you do it right.