On a Christian site, someone said that it is a sin to wear a bikini. I do not agree because I went sailing the other day and I was the only one not wearing a bikini and the men on the boat did not gaze at the women wearing bikinis. I do not think bikinis are immodest because they can be appropriate when swimming, just not for walking around on the street or other public places.
I would like to direct you to Wendy Shalit’s book A Return to Modesty, which covers the subject of modesty (and immodesty) better than anything I’ve ever read. It is consistent with a Christian world view even though the author is not a Christian.
In my opinion, wearing a bikini is sinful under most circumstances because the purpose of it is to show off as much flesh as possible while still covering the absolute essentials of genitals and nipples. There is nothing God-honoring about bikinis and much that is gratifying to the flesh: for men to leer and for women to show off their bodies. Scripture calls us to live and dress modestly, not to gratify the flesh. It calls us to do everything to the glory of God: wearing bathing suits that are designed to cause men to lust and women to publicly display their bodies is the opposite of glorifying God.
If the men on your sailboat didn’t gaze at the women wearing bikinis, I would suggest that they may have been desensitized. Or perhaps they were just wearing sunglasses and you didn’t notice their eyes! <smile>
I will add a disclaimer. There is nothing at all sinful in a wife wearing a bikini if only her husband will see her in it. Showing off her body to please him is part of the pleasure of sex that God intends for married couples to enjoy. See “The Song of Solomon” in the Old Testament for biblical evidence of that.
I’m glad you asked.