I've never done more than a 1650 yards (1500 meters) in competition, but every year my high school swim team does an hour-long "marathon swim" and I have the record for that, 4750 yards. I also really like the 400-yard IM, though I'm not fabulous at it, and I really, really, really want to try the 200 fly. But my absolute favorite event is the 500 free. Yay to see another distancer!