I'm a swimmer, and so I shave my chest before a meet for added speed.
Only problem is that although the skin is completely smooth, you can
easily see the black hairs underneath (kinda like blackheads). I
always see these perfectly hairless guys with not hair showing beneath
the skin.. How do they do it? Is there some kind of cream or bleach
that hides these hairs beneath the skin?

By the way, I'm not looking to do anything else but shaving, so
epilatories or anything like that is not an option.

Thanks!

What colour is your skin? My skin is quite fair, and when I shave my
legs I can sometimes see the little black dots under my skin where the
hair still is. I'd say the other guys most likely wax or use a
depillatory cream, rather than shaving.

Um, you can't shave the hair under the skin, so you're always going to
see those little black dots under the skin. It's either small hairs,
or your actual hair follicles which you'd need to rip out with wax, or
destroy using depillatory cream.