People who are serious about endurance sports don't train at the gym, at least not if they have a choice. They go on runs and rides with their clubs, or get their swimming instruction and lap practice elsewhere. If they have the money they go to places like
Breakaway Performance Center. If not, they wing it on their own. You will only rarely if ever catch them on an elliptical at the gym!
Serious body builders however go to the gym. It's to them what the pool is to a swimmer. You won't find body builders in the pool, and if you do - let's just say they're not the most impressive performers. I often go to a pool that's part of a gym (it's open 24hrs, its main redeeming quality), and there's a mix of good swimmers, non-swimmers, rank beginners - and the occasional weight trainer. You can immediately tell who is going to churn up the storm of the century on their 'fast paced' 1:00min 50m lap, then stand around. Churn another half lap. Stand around. Then get out and leave because they're exhausted. (Meanwhile the competent swimmers turn 35-45sec laps for an hour.) It's like a tradition. These are usually also the only people who won't talk to the serious lap swimmers, like they look down on us or something. Everyone else is pretty nice and friendly.