Ok, this forum isn't dedicated to discussing drug use, whether the subject is related to sex or not, so I'm gonna lock this thread. For the record though, I'll clear up a few things you guys need made clear for your own well being.
Ecstacy does cause damage to your brain. It can cause chemical imbalances, mostly to do with seratonin deficiency/increase, which can result in depression, mood swings, or in some cases people become "E-Tarded" and end up with a constant sense of happiness, usually combined with reduced reasoning abilities. These are the moderate to severe effects, but there are many mild ones as well.
If you're interested in learning the
FACTS about this or any drug, I refer you to the site that myself, along with many many people I have encountered in the drug culture used,
http://www.erowid.org/chemicals/mdma/mdma.shtml. This is an incredibly factual and reliable site, with details on basically every drug you can think of, so if you need your questions answered, go there for a full list of effects, side effects, testimonials, etc.
I'd suggest you don't swim while on any drugs, as they can cause you to become relaxed to the point of accidental drowning, as well as sometimes causing vertigo in a weightless situation, not to mention that sometimes your perception is skewed and you are no longer in a state of mind to assess a situation appropriately.
What I've heard about sex on ecstacy, is that it is the best sex you'll ever have and often people claim that it ruined sex for them afterwards, because nothing was ever as good again. Otherwise, you are perfectly
physically capable of getting an erection, although sometimes the psychological effects may inhibit it.
Remember that if you are going to experiment with things like this, to do it under consentual circumstances.