I assume the one you're referring to is the v shape of the lower stomach from the naval area down to the pubic area. Ask one of your female friends if you have one if you can't see it yourself and yeah you can see it if you're wearing like bathing suit trunks.
its the "v" shaped outline in your lower abs. If you're facing a mirror the top of the V is around your hip bones and your d*ck would be the point. I can see it on most guys if they don't have a shirt on, the pants don't have to be that low or anything. Most people call it a 'swimmers v'.
If you're at all slim (like me) or fit, then you will have 2. There will be one on the lower edge of your abs, then around at the corners (sides) of your waste going down. If you can't find them, then might not be slim enough or the body to have them.