I have a pair of swim briefs that I have had for almost 15 years and since they still fit I keep wearing them. It was earlier this year when I realized something about them. I assume with the waterslides I have gone down that the backside had gotten a little worn down. With them off me they seem like there is nothing wrong with them. When I put them on the material stretches. With the material stretched over my ass they are extremely sheer and you can see my whole back side. I didn't realize this until I went into a washroom at a beach and passed by a mirror and had to take a second look at what I thought I saw. I could see my whole ass including ass crack. It was like I was wearing nothing over my ass. I don't know how long I had been doing this and it probably was for years. I had many people give me looks and now I can guess what they were looking at.