The "cut" thru the reef is plenty deep and boats steer clear. If that's what you call "a seam"?
The gap out from the shore to that cut, or coral heads, that is no problem if you have divers of sufficient self control and navigation skills. Popping to the surface due to any lapse in buoyancy skills in shallow water or the need for a visual navigation siting can be problematic as the passing boats...no way could they see a diver in time at that speed. A whole lot of divers "fail into" that category, lacking skills.
The real point of my additional post with image.... It simply is not as close as they infer or you imagine being conveniently possible. It is, as I like to say, "quite a thrash".