God gave us beautiful bodies, He made us in His image. Showing our forms or even showing skin isn't a sin. If we are displaying ourselves in a way to make other people lust for us, or to be vain, or indecent, then God has a problem with it. I've seen women who dress modestly, show a little skin, but do it in a beautiful, mature, and artistic manner. I've seen nude models for art students who aren't naked to create lust, but to show the beauty of the human form. God created us naked, we are born naked, so I don't think nakedness is wicked. The most passionate gift God gave for married couples to experience is one where we are able to appreciate the human body.
Using nakedness or skimpy clothing to bring yourself or other people to sin is wrong. I dont' think I'm going to hell for wearing short sleeves and a skirt that doesn't go past my knees. I don't think people are going to hell because they show their ankles or leave their faces uncovered. I don't think married couples who enjoy each other's naked bodies are doing anything wrong.
Satan has corrupted every gift God gave us and twisted it to bring us away from God. Even something as beautiful as the art God made our bodies into has been corrupted into something shameful and wicked. Sex is something that has to be talked about in whispers and has been twisted into something dirty and disgusting. Most people attribute talking in tongues to being a satanist. Even the pharisee's who saw Jesus casting out demons decided it was the work of satan.
We need to examine the intent in a lot of our actions. Most of the time things and actions are not evil unto themselves, but rather the intent is evil. Are you using your bathing suit as a utilitarian garment meant to cover private areas of your body and protect your skin while swimming. Or, are you using your bathing suit as a way to make other people lust after your body, feel ashamed of their own bodies, or to make people look and admire you for your own vanity?