YOU'RE SITTING on a beach in Mexico. The ocean is shimmering aquamarine, and pelicans dot the shoreline. There's a dark, well-built man in front of you with whom you're having intense eye contact. You're both alone. The sun is blazing and you're dripping with desire. Finally, he approaches. He sits beside you and without saying a word, gives you a long slow kiss. He's now caressing your entire body with his lips. You push him back on his towel, pull down his swimsuit and . . .

Hey wake up, babe! Nice fantasy, but this is the '90's. You don't know where this guy has been and even if he told you, who's to say you should believe him. Having sex these days is like playing Russian roulette. According to the World Health Organisation, there have been a million new cases of HIV worldwide since mid-1992. Tell that to the Pope. What's more, AIDS is rapidly increasing among women. By the year 2000 the majority of those newly affected by the virus will be female.

Since females are more likely to get it from males than vice-versa, these are frightening statistics for today's active woman. It kinda makes you not wanna have sex . . . kinda. But if we choose to remain sexual creatures, we must grow up and take responsibility, or we may not get the chance to grow up at all.

So what's a girl to do when the man of the moment says he won't or can't use a condom? Mutual masturbation is an option, but if you're even slightly serious about each other you run the risk of getting tendonitis. Of course, there's always celibacy. But the reality is that it's not the popular alternative.

So get ready for another Reality: the female condom. That's right, it's the first birth control method under a woman's control that helps to prevent sexually transmitted diseases (STDs) including AIDS. Hallelujah, praise the Lord. I mean, isn't the world dangerous enough without having to worry about dying from pleasurable activities?

Sure you agree, but before you go running to the closest drugstore, you should know that the female condom is currently being sold as Femidom in the UK, Switzerland, Austria, Portugal, the Netherlands and Norway. In development since 1987, Chartex International, the London based company who holds the patent, will be making it available throughout the rest of Europe by the end of 1993.

In the U.S., Mexico and Canada, where marketeers got a bit cerebral, this new device will be sold under the trademark Reality, a sobering moniker for even the most pragmatic romantic.

But exactly what is this new contraption? The female condom is a thin sheath made of polyurethane and two flexible rings. One ring lies inside the closest end of the sheath and is used to insert the device and hold it in place. The other ring remains outside the vagina during the act of sex. As the vagina expands to fit the penis, the slack in the reality sheath adjusts with it.

Granted, the thought of a ring dangling outside of you is not exactly a turn on. But certainly this isn't the first time men have had to jump through hoops to get to you. Once you're into the act, the female condom isn't all that bad. (Although you may want to have a few drinks before you try this at home.) Reality is about as easy to insert as a diaphragm, but it's smaller, and it comes prelubricated. It's also disposable, (to be used for only one act of sex) so there's no clean up afterward.

The press kit says Reality "doesn't significantly inhibit foreplay," and that unlike the male condom you can insert it up to "several hours before sexual intercourse." Nevertheless, it's not the type of thing you'll want to wear out to dinner. And unless your beau likes fondling polyurethane, you may want to insert it after some foreplay.

The kit also says Reality "must be removed before standing up." This sounds like a potential problem, unless you're totally into the missionary position. The directive is not meant as a hazardous warning, but rather deftly avoids stating that one may end up with sperm dripping down one's thighs. There are creative solutions to this dilemma, but I'll leave you to figure them out.

In trying this product, the only thing with which I found fault was the 4-step illustration on insertions and positioning. Although the last step simply notes "Reality in place," there is no word on precisely how much condom should be left dangling. I'd advise experimenting when you're not ovulating. Like its male counterpart, the condom can end way up in innerspace, meaning the sperm are free to explore your love canal. Experience says to give it some slack and not have the outer ring pressed up against you.

Incorrect use is said to contribute to the pregnancy rate, estimated to be between 21% and 26%. This estimation is based on doubling the 13% rate for a six-month testing. It should be noted that after one becomes adept at using the device, the actual figure is believed to be closer to 5%. This means that, with proper use, the female condom can be more effective than the male condom, which can have a pregnancy rate as high as 15%. (Because the male condom has been around so long, it has never been subjected to such rigorous testing.)

Statistics show that 80 percent of men like Reality as opposed to 75 percent of women. My partner in this experiment preferred it to the male condom because, he said, "it's less constricting and you feel more natural." It's also thinner and stronger than latex, and conducts heat more effectively, which can be helpful.

Only 20% of couples surveyed use male condoms. If you're among the many who don't, it's reassuring to know you have another option against preventing STDs, AIDS and unwanted pregnancies. At about $2.50 a pop, Reality is three times more expensive than the male condom. "That's about $30 or $40 for a weekend," my friend said. Perhaps, but it's not all that much if you value your life.

Reality will be sold in a box that includes three separate sealed packs (prelubricated) and a tube of extra lubricant. I'd say that's a great gift idea for under $10.