Sand sharks are common in Florida from Tarpon Springs to Naples. They feed, expel waste and spawn within the sand bar close to shore. Been doing that since the ‘50s (that I know of). They don’t normally attack humans, unless provoked.
I used to swim out to a reef, poke a sea urchin open with my spear, swim back about 20 feet, and then watch the feeding frenzy. The little fish would immediately attract the bigger fish and so on outward. Then you would just shoot a big Drum, Jack, or Shark. Then I would drag the thing to the beach and someone would pay me $20 for the fish and I would use the money to go buy pizza and beer.
Now that I look back on it I suppose it wasn't the smartest 200 yards of swimming dragging back a bleeding out big chunk of meat through the reef, shallows, and surf.