Not long ago, on a scuba diving trip, the dive guide reminded us a person at the water's surface would resemble no more than a partially submerged head of cabbage, not a full body like a pedestrian crossing the street. I once witnessed a popular sailing instructor "bump" a snorkeler with his dinghy in an anchorage at Peter Island. Luckily no one hurt, except for their feelings. I guess both swimmers and boaters are reminded to pay attention to their surroundings.