It's all relative, of course, to how mature you and your friends are, physically and mentally. There are some young kids that can handle pretty extreme stuff with sense and maturity. I've also known some 40+ year-olds who probably should never have been let out of the house.

Personally, I'd say that the average 12-year-old male has seen far worse material than ANYTHING in El-Hazard by borrowing his friends' porno mags and reading them under the bleachers at school - an activity which very rarely scars 12-year-olds for life.

So, if you and your friends are 12-years-old or older, you should be fine. Your parents may disagree; I don't know. It depends on your parents. Mine probably wouldn't have objected when I was 12, but I have unusually tolerant parents.
Here's a general listing of "questionable" material in El-Hazard, most of which has been mentioned by people already, from what I consider to be "worst" to "least":
1. Episode 13 of "The Alternative World". Many scenes of the female (and male) cast bathing in the nude. There are no fully exposed breast shots, but there is a scene depicting Fatora and Alielle (in disguise) fondling most of the female cast in a rather sexual manner.
2. Episode 3 of OAV1. Several scenes of the female cast bathing, including a few that show breasts.
3. Episode 2 (I think) of OAV2. Alielle and Fatora splash around in a spring nude.
4. Episode 23 (I think) of "The Wanderers". Rune Venus and Nanami splash around in a spring nude (and with far more innocent intent than Alielle and Fatora

).
5. Episode 2 of OAV1. Alielle reaches into Makoto's underwear and grabs "Makoto Jr.", after crawling all over him in a very seductive manner (some of which happened in episode 1, as well).
6. Episode 2 of "The Alternative World". Fatora reaches into Parnasse's underwear and grabs "Parnasse Jr.", after crawling all over him in a very seductive manner.
7. Episode 6 of "The Wanderers". Shayla is displayed nude, with Makoto's and Fujisawa's heads blocking the "naughty bits" from view.
8. Episode 3 of "The Wanderers". Rune Venus bathes wearing a rather sheer and clingy bathing outfit.
9. Just about any episode featuring Alielle in OAV1, OAV2, or "The Alternative World" will have Alielle behaving like a nymphomaniac lesbian at at least one point. 'Cause, really, that's what she is.

10. Just about any episode featuring Fatora will have her going as far as she can with Shayla, Nanami, or (rarely) Afura. She normally never gets any further than a kiss, though.
All that said, it would be difficult to simply skip any of these episodes (particularly episode 3 of OAV1 - one of the worst offenders on this list). In addition to having questionable material, they also generally feature important plot stuff. If it's too much for you and your friends to handle, I'd suggest waiting a couple of years. You can use the time to save up money and buy the box sets.
