tonight on "nightline," end of monogamy? the biggest trend in marriage, say some studies is cheating. now meet the real-live young couples who say hooking up with strangers is saving their most intimate relationship. the gummy bear, the latest must-have in the breast implant industry is a controversial new model nicknamed for candy. some doctors say they're safer and more authentic than the alternatives, but what's the real story. and bruce 3.0, while his ex-wife has been busy making headlines, he's been busy with a new movie and a new baby.

he'll tell us how to stay happy in an unconventional extended family. >> good evening. i'm bill weir. tonight it's the young and the restless. 20-somethings who are married or in committed relationships, who say their unions are more secure and more honest because they don't believe in monogamy. they say it is possible to be devoted to a special someone while giving in to karnal urges with anyone. are they kidding themselves? to find out, juju chang dared enter a modern twist on a swingers' club. >> reporter: welcome inside a highly provocative penthouse cocktail party. >> i have been dying to wear this skirt. i bought it a while ago and i've just been wanting to wear it. >> mite line gained access to

this swingers' party in manhattan. these couples are looking for a night of passion, and they speak very passionately about what they do. >> we're excited. >> yes, we're finally here. >> national surveys, suggesting roughly half of american marriages someone's cheated. these couples are part of a dramatic shift in younger couple's attitudes on infidelity. one study shows an increase of 20% of young wives cheating and and 45% of young husbands cheating. steve and janel have been a couple for two years. she manages property and he's a deejay. they engage in soft swapping, which is everything but full intercourse. >> there's stuff people do that we want to try. >> michael and sara do full swaps including intercourse, but they don't kiss other couples. >> the kissing is more intimate, and we like to keep that for us.

>> researchers point out that younger couples are marrying later in life and come to the marriage with habits acquired over years of dating. among them, sleeping with other partners after the initial attraction wears thin. >> how did this start? >> we made a bet with the super bowl. if the patriots won, i got a to get with another guy. needless to say the giants won. >> reporter: isn't it odd to see your mate with another person? >> we're not really the jealous type. >> reporter: these are mostly young couples prescreened based on attractiveness and age. >> this is swing school and it's how we welcome beginners. tickets are around 200 dollars.

it's perfectly legal and everyone practices safe sex. single women or couples are allowed, but no men flying solo. men can of course talk about what they want, but make their decision what they want to do and what they don't want to do. the women aren't just setting the rules, they're driving the explosive growth in the online swingers' market. >> this is the new generation of swingers. 5 years ago adult finder. the majority of traf sick women. >> they're the one wros reach out to the other couples on the site and decide who's safe and who they want to play with. they're the ones driving the interaction and finding the right people. >> just look at ashley madison.com, listing 14 million people in 22 countries looking to have extra marital hook-ups. coveting thigh neighbor's wife

is as old as the bible. hel senn an anthropologist who studied sex and adultery for years. >> we're predisposed to fear when an animal is running towards us and same thing towards adultery. >> as night falls, the room gets darker, the mood sexier. scommik sara have scoped out the room. >> there's an asian couple we're looking at it. >> we're going to take it to the next step, i believe. >> they start to get frisky, kissing each other, hoping to get things started. it quickly gets a little too sexy for our cameras, so we retreat to our private interview suite where couples let us know what's going on. so what happened? >> sara and i commandeered one of the couches and then somebody else came over and joined in. >> so she started kissing you. you kissed her back, then what happens? >> the magic happens.

>> you had sex with the other woman, and you had sex with the other man? >> yes. a lot of older people, their families are very traditional, you sleep with one person forever. but in today's day and age, things are not the way they used to be. >> reporter: michael and sara fill us in on their full swap. >> i really get turned on watching michael please somebody else because i know how well he pleases me. and at the end of the day, i'm going home with him. there's nothing better than us. we please each other so well. >> for janel and steven, it wasn't exactly what they were hoping for, but the night is still young. >> reporter: what happens between the two of you when you get home? >> oh, it's on. that's allky say. >> reporter: they may be breaking sexual tab boos, but they still don't kiss and tell. coming up next, it's the new frontier of breast surgery. introducing the gummy bear

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now we take you to the cutting edge of breast implant surgery and a controversial new silicone implant, nicknamed the gummy bear. for medical and more commonly cosmetic reasons, hundreds of thousands of american women get implants each year and after decades of uncertainty about the safety of those, one new model has women flocking to the doctors' offices with questions. and abc's david wright goes in erch search of answers. >> reporter: in the ongoing quest for perfect breasts, some say it's the holy grail. aubrey has come to dr. grand stevens for a do-over. >> i want gummy bear books. >> reporter: gummy bears. a funny name for a different type of artificial breast. their stevens says gummy bear implants look and feel more like the real thing. >> this is a gummy bear breast implant. >> reporter: more than 300,000 american women a year undergo

cosmetic breast surgery. some of them for the second time because the first time she didn't like what she got. >> i want something that felt more natural, this is my body, and i don't want something fake. >> you want something that's fake, but doesn't feel fake. >> exactly. >> reporter: demand for breast surgery has tripled over the last 15 years. aubrey is among the women who report their new breasts feel unnatural. others report leaking or sagging or hardening. many have to go back for new breasts in fewer than ten years. but according to the doctor, the gummy bears are different. why is this different? >> the gummy bear breast implants are new to americans. they're form stable, they keep their shape. >> reporter: the new implants, approved for use in march are

ma -- they are touted as implants too keep their shape even if they're cut in half. >> it's sticky. >> you can turn it upside down and they're not going to go anywhere. they act like gummy bears. let's call them that. >> reporter: for years, they have been available in the u.s. only to patients willing to take part in a clinical trial through surgeons like dr. stevens. but breast surgery is a sensitive subject. whenever any new product is introduced, there's a really question of safety. there have been problems in the past. there was a moratorium for about 20 years, given concerns that ruptures might increase the risk of r cancer.

europe is in the process of a recall from silicone implants. thousands of women are having the implants removed over concerns they tended to rupture. but the fda says it's confident the newly approved implants are safe. after an eight-year clinical trial. >> so a car accident, direct trauma, right? >> right. >> reporter: he says, they're tougher to rupture. >> this from unscientific experiment, they do seem pretty sturdy. >> it's going to take a lot more trauma than your chest would withstand. >> he swears by the gummy bear, but others say, not so fast. the fda approval of these devices is contingent on follow-up studies to make sure they're safe over time. dr. grth garth fisher says the

latest and greatest may not always be the best. you may recognize him from keeping up with the kardashians. >> i love you. >> i know garth fisher is the best plastic surgeon ever. >> fisher doesn't like gummy bears, which he says are no subs tul for superior surgical skill. >> i think for some doctors that need that shape because they're not able to create it on their own, i think it's a good match for them. >> reporter: how is anybody supposed to know which one is better? >> this doctor, author of behind the mask, beneath the glitter. >> you can't say a rolls-royce is better than a ferrari. they're both cars that get you from a to b, but they have different characteristics. >> reporter: then again, you might not need either a rolls-royce or a ferrari. plenty of women would say indulging the quest for

perfection may not be the road to health or happiness. i'm david wright for "nightline" in los angeles. coming up, with a new daughter and a new movie, how bruce willis stays centered. e that could adapt to changing road conditions. one that continually monitors and corrects for wheel slip. we imagined a vehicle that can increase emergency braking power when you need it most. and we imagined it looking like nothing else on the road today. then...we built it. the 2012 glk. see your authorized mercedes-benz dealer for exceptional offers through mercedes-benz financial services.

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pride always hurts, never helps. such was the advice given to bruce willis's character in "pulp fiction." while the leading man has plenty to be proud of, half a dozen new movies this year, a new baby and a genuine friendship with his ex-wife, demi moore, it may be the avoidance of pride that makes all of the above actually work. >> reporter: bruce willis is the red carpet candy at this year's cannes festival, just finished filming die hard five in budapest. and moon rise kingdom, open at the most prej tijious film festival on earth. we sat down on a sunny rooftop above the fray. >> just to do this part of the interview with the shades on. >> reporter: bruce says he's

happier than ever, he and his wife having just had a baby girl. >> you're looking remarkably good. >> do i look tan? >> reporter: you look well slept. and more kids? >> too early to say. too early to say. mabel ray is only six weeks old. >> reporter: different from the last three? i mean, how does it compare? >> a little different and a lot more of the same. changing diapers like a champ. >> reporter: the other three are his daughters with demi moore. the couple split in 2000. >> reporter: you managed to somehow make your life work after a divorce with kids. you've all stayed friends. how is that possible? >> if you just put the kids first, everything gets a lot easier. knowing they still need care and attention and love all the time. >> reporter: and put your ego aside? >> ego is dead. >> reporter: ego also gone from his latest role, captain sharp

in moon rise kingdom a cop on a fictional island in 1965. >> what do you have to say for yourself? >> reporter: your hair is an awesome actor in all this. >> i'm deputizing the little guy. >> you saw the absence of vanity, not a vain guy, and hair being what it is these days, i like my hair. >> reporter: and of course he's coming back at john mcclain for a fifth time. >> welcome to the party, pal! >> reporter: why are you keeping on going back to him? >> the competition is with myself to try to beat the first film. >> reporter: is he donning the famts undershirt again? >> no, not yet. it's yet to be seen whether we goat down to it or not. but we're just having that conversation now. >> reporter: but the focus now is moon rise kingdom, a sweet tale of two young kids who fall

in love and run away. while the melancholic adults watch their own loves tarnish and fail. >> does it concern you that your daughter's just run away from home? >> it's sad and sweet, but even sadder that these people have gotten to the age they are and they still can't figure it out. >> reporter: do you feel you've figured it out? >> i figured it out this time, anyway, that keeping it simple just makes things a lot easier. >> reporter: did you ever take things seriously? >> yeah, probably. >> reporter: is this part of having a new baby? >> yeah, i'm sure that's some of it. i just allow myself to not take things seriously and to not give it so much heat and give things so much noise. >> reporter: these days bruce willis seems less john mcclain. >> that's going to wake the neighbors. >> reporter: and more captain