Broadening shoulders at 22 years old and gaining endurance.

I'm a 5'5 male (._.). Will swimming broaden my shoulders at this age still? I was on the high school swim team many years ago, but was never any good at it due to my endurance. My shoulders are wider than most guys my height, but I'd like it to be a little bit bigger still. I would like to get back into swimming, but the problem is my endurance is absolutely horrible. During swim team I had to take so many breaks, it was bad. I actually have no clue why my endurance never really improved. I was swimming with some people the other day who barely swam or worked out and they can swim longer than I can. I don't know whats up. I get tired too easily. This was one of the reasons why I chose weight lifting to stay in shape, because I didn't have to run or swim. I have a pretty nice body from weight lifting, but I think I would like to swim as well. I think I would look good if I weight lifted and swam. 300 meters continuous is all about I can do. When I was in the swim team, 500 meters is a bout all I can do.