KSH, I was the same swimmer in high school. I loved doing the 500 free, and people thought I was crazy. I also wouldn't place at 1st, but would do well and felt good at the end. I'm not a sprinter at all, so I think we're pretty similar in terms of athletic genes. I can go long and far on my bike, which is why I'm trying to get into doing brevets, etc. I can sprint only for short distances and I absolutely die after. But I also haven't trained properly to develop those muscles. So part of it is just my style. Keep at it!
"Only the meek get pinched, the bold survive"