In that area of the Bahamas, where it's mostly hard white sand flats, when it's sunny they are easy to spot. You see their dark shadow. Or, when the move from deep water and first enter the flat, you can spot them because they're still a darker color. (They change color as they spend a few minutes in a new environment.) same with mixed turtle grass/sand flats--you can see them when they move from dark to light, because they are darker/mottled. But if it's cloudy/overcast, it can be very difficult, and often by the time you see one, it's too late.
Hooking one is a different challenge. You can't cast too close, or they will spoil. You can't lead them too much, because they change direction a lot. And you have to twitch the fly at the right time--so they see it, but don't get spooked.
If you do hook one, assume that a shark will be following in short order...