Is Swimming Anaerobic?

Depends on what swimming you're doing, but if you're going out there and swimming easy the right way its aerobic. Obviously if you're doing reps and such in the water its anaerobic.

Monitor your breathing is all.. Long easy or steady swims are aerobic, just like running. Short, fast intervals are anaerobic just like running.

Who gives a shit? Swimming is better exercise than running. And male swimmers have totally hot bodies!

Only if you keep your head under.

Swimming is cross-training which uses different muscles (assuming your primary sport is not swimming, e.g. running).

I have a hard time imagining how it could be detrimental to your running development.

I was thinking that it could be a detriment aerobically, not muscularly.