There was a father/daughter team diving in the Key’s, she was a small girl wearing dads hand-me-downs dive gear. The BC was too big and she was overweighted so she moved thru the water almost vertical fining up the bottom and kicking the reef whenever her father stopped to take pictures. I suggested he work on her trim so she could get horizontal and get a better view of the reef. He lashed back that she likes swimming that way!
On a trip to Roatan a woman in our group was swimming the same way. Back on the boat I told her (quietly) she was overweighted and should try taking off a few pounds each dive. After she finished steaming over this guys rude remarks she figured out I was talking about her gear, not her. By the end of the week she had shed 8 pounds of lead and was grinning ear to ear when she saw me underwater.
Another no-no is waking sleeping Parrotfish with your lights, circle them, don’t highlight them or cook them with your HID! They can only make one cocoon per night that protects them from predators. Since most night dives are really twilight dives they are now open to attack the rest of the night!