Poor buoyancy control is a valid criticism of divers around the world. The ability to control ones buoyancy precisely is neither magical nor natural grace... it is only a practiced technique. Piggy divers tend to overweight themselves and compensate by inflating their BCS, they lose all buoyancy control and drop like anvils onto the coral.
Poorly trained piggys swim in the overweighted (head-high, legs-down) attitude that causes their fins to mow down the corals as they swim over the reef. Precise buoyancy control is the hallmark of an experienced reef diver. When hovering in the horizontal position, his fin tips point upwards away from the corals. Body-positioning and mid-water buoyancy skills result from training and practice. Conscientious divers use only enough weight to neutralize the bodys natural buoyancy, and develop the slow, relaxed breathing essential for zero-impact diving. Remember to never hold your breath.
You are ideally weighted if, at the end of a dive wearing a nearly empty tank you can hover motionless at a 15' decompression stop without inflating your BCD.