Should a Christian woman wear a bikini? Only if she wants to blend in with all the other woman wearing bikinis, so that the beach looks like a cacophony of female body parts wandering around! So probably not. Wear a classy one piece and stand out!
So I ended up writing a lot! Please critiques are welcome, just make sure they are done with Christian charity! Its not perfect, but just my thoughts that probably need some re-arranging and polishing.
Modesty, like chastity, is a very misunderstood virtue. Just as most people mistakenly think that chastity is the art of not going too far, so they mistakenly think modesty is the art of not exposing too much skin. Not exposing too much skin of course is a part of modesty, but it is just one part. Modesty, like chastity, is not merely a negative defensive virtue, but rather a positive inspirational one.
Lets remember why we wear clothes- to protect us from the elements (no one wears just a bikini in Antarctica), to protect our dignity, and to express who we are.
Ill assume we are all ok with the first and move on to the second, where I have to agree with Gerald. Hunter gatherers usually just cover their private parts, leaving the breasts of both men and woman exposed. Thus I tend to think our dignity, whether male or female, is guarded simply by wearing a pair of shorts that goes down to near the top of the thigh. Yet while this is sufficient to guard our dignity we find that in more advance cultures we cover up far more. Why?
I think that it has to do with the third aspect, expressing our interior disposition. The pair of shorts is sufficient to guard our virtue, and serves as our defense. But modesty again is about inspiring us to deeper holiness, and so causes us to look at the person in their fullness. Thus the clothes must cause us to see the entire person and convey the person, body, mind and spirit. The cut, color, fit, and textures all play parts that help us achieve that goal.
A lot of people have been linking Jessica Reys swimsuit line, http://www.reyswimwear.com/ and I think that is a good place to start. They are actually two piece but visually one piece. They most probably show more skin than the trashy French maid costumes some people have mentioned. Yet the feeling between the two is vastly different. If I were to look at the costume I would start to feel lust; physically I would feel a pent up energy that builds up inside of me. Thats because it is visually designed to do that! So of course I avoid looking in the first place. But when I look at Reys models I get a different feel. The energy does not build but rather flows gently. I have no need to release. Its similar to the feelings I get looking at classical art (or looking at pictures of Audrey Hepburn, after who Rey modeled her line.) Why the difference?
The French maid costumes typically show both cleavage and her upper leg, while the swimsuit only shows the leg. The other thing is I get the feeling that the costumes are often designed to tempt a mans eyes up the skirt, but I dont get that feeling with the swimsuit. This is because the suits are clearly defined and a man knows where they stop and there is nothing more he is able to see, so his eyes are actually directed to either her arms or her face (Its always good to look at her face.) Also all the suits, while they clearly define her figure, have plenty of folds, and folds add interest in an artistic, aesthetic sense. The reason superheroes in comics are drawn in skin tight outfits is because its a lot easier than drawing regular clothes with lots of intricate folds, but great master artists love drawing folds because of the life and interest and depth they add to the painting. So folds in a sense bring life into the suit, a life which reflects the life and even the depth and complexity of the woman wearing it.
I want to talk a bit on the word provocative. We use it a fair amount in fashion, and I want to look into its meaning. It comes from the Latin provocare. Vocare is the root of vocation- a call, and it means to call forth, often used on the battlefield. Pro-vocare is a challenge. A woman dresses provocatively often means displaying some of her breasts, midriff, and/or upper leg or even the pelvis area in specific ways. Pro-vocare is like hot sauce- a little every now and then is ok, but a little goes along way. When I go to the beach and there are 100 women wearing bikinis I just go numb.
First off, I dont ever want to see a womans pelvis area unless I am married to her. I mean of course the very skimpy swimsuits. As a general rule Id avoid the midriff. It just is the least classy of the three, and it breaks up her core, which puts the focus on the wrong areas. If a man sees some of a womans breast every now and then hes like huh, breasts! which comes from his primitive, reflexive part of the brain. He then goes his merry way if hes virtuous. Showing part of her breasts I think is always provocative. But a womans breast has two strikes against her. They dont actually do anything. That is she cannot really use them to express herself. Also, if a man is talking to face to face his eyes can wander to her breasts. While he should have enough control so this does not happen, again there is a part of a mans brain that will be drawn to look down, and must be resisted by his will and his virtue.
Legs have advantages- she can use her legs to express herself, and of course when looking face to face its too far to look down. At a distance they are part of her body that again can express herself. And while her upper legs can be provocative, in Reys suits I dont think they are.
This is actually a key point I think. Is the womans body seen as an integrated whole that expresses who she is in her completeness? Then it is love and beauty. Or is she just a collection of parts meant to satisfy a mans selfish desires? Then its lust.
Bikinis, especially skimpy ones, do the second. The top part frames and shows off her breasts. The bottom directs a mans eyes to her private parts. Thus a man is invited to look back and forth from her breasts to her private area, and avoid everything else. In a very real sense it dis-integrates the woman- breaking her into several pieces. This is in contrast to the Rey suits, which directs a man to her legs or arms (which are beautiful and expressive of her life and personality) and her face, which is of course the most respectful place to look. Her body core is portrayed as feminine, alive and attractive, sensual but not sexualized. In fact, the swimsuit is not so much provocative as evocative. It shares the same root, vocare, but instead of a challenge it means to summon forth a spirit. In this case its a spirit of beauty and life that is actually summoned forth through or perhaps into the man. This is the positive, inspirational aspect of modesty directed from the woman to the man.
Wow. Lots of stuff there! So regarding what to wear in the bedroom. Let us start off by acknowledging that the husband and wife are meant to be gift to each other. The husbands body is now his wifes, and the wifes is now her husbands. But this is not a one shot give away, where now you have my body so you can do whatever you feel like with it kind of relationship. Rather its marked by the continual exchange of the gifts, which means that the husband initiates relationship by giving of himself to her, and his wife responds by giving of herself in return. This giving takes their entire lives, because they have their entire life to give away! If their marriage is to image the marriage of Christ and the Church, their love, that is their giving, cannot be forced. It must be their continual free choice! This requires a great deal of trust!
Therefore man should never force his wife to wear anything, whether good or bad, but should let her know when he see her wearing something particularly beautiful, at which point the woman can freely chose wear that. Of course it is wrong to force her to wear something that she finds distasteful. But when this happens there is something wrong, a disconnect, that needs to be addressed. Either the man has asked his wife to wear something that is objectively distasteful, in which case he is at fault and needs to repent and convert. Or he has asked his wife to wear something that indeed highlights her natural beauty and that is objectively tasteful. In this case she needs to repent and convert.
I cannot see French maid costumes as anything but distasteful. If it has been sexified it will portray the wife in a dis-integrated way. In addition it alludes to the wrong story, the story of the sexy maid who seduced her rich employer. They are playing parts that are antithetical to the parts they are called to play. The husband and wife along with the Holy Spirit are called in a sense to play God, that is make a mini image of the Trinity himself. When they play God in this fashion their love, just like Gods, can create new life. Any outfit which tells a story contrary to this image should be avoided. Costumes that reflect this image or at least cooperate with it can be used freely (if that is their thing!) In addition many bikinis as well as much lingerie would not be appropriate since they portray the womans body in a dis-integrated way. Such outfits are pro-vocative. They effectively encourage lust in the man. He may be able to resist, but its tempting him un-necessarily. Whatever she wears should present her as a unified, integrated whole, body and spirit!
Conversely, suppose a wife refused to make love in anything except a muumuu, or some long underwear. In this case she is guilty of being (in a term I take from Dr Greg Popcak) piously dumpy. She is forcing her husband to look past an unappealing exterior to find the beauty within. This is actually immodest, because again modesty is not merely protecting our virtue but to act and dress in a way that inspires others. Love calls her to dress in an e-vocative fashion, because that is what will lead her husband to God! In this sense she is the one who sins, or at least does wrong.
Again, very important point- the husband does not so much command as lead his wife. His lead is not meant to achieve his own selfish ends but rather to lead his wife to her joy. In following she finds her joy and the man has his joy in hers. This means that regardless of how tasteful and appropriate an outfit is, if he tells her she is beautiful due to his own selfish desire that she wear it to please him, then he sins. But the virtue of tasteful outfits is that they inspire us to proclaim their beauty in a disinterested fashion.