Should I not go swimming with my sister in law because of my interest in women wearing swimsuits?

If you have a wife and are looking elsewhere and getting kicks from it that is the same as porn. Scripture says that to commit it in your heart is the same as committing it in reality so you are being unfaithful to your wife in the form of adultry no matter what way you slice it or cap it off aws being a good family man. Just food for thought but you are allowing yourself the luxury of being bad and then finding excuses for not calling it that and that is no different than the unfaithful husband and Scripture says so. You need to get your eyes on your own wife alone and do whatever it takes to get rid of the rest of the desires or risk losing it all. The more you let your eyes wander the more you will desire and it will change how you feel about your own wife. Proverbs 5:15 says that when you are to drink the water from your own cistern. Another one says that if you drink from someone else's cistern that your own well will go dry. For the sake of your marriage I would stop allowing your eyes to roam and your thoughts to wander.