Whales -- The longest time a humpback whale stayed under water was fifty-five minutes. Some years the humpbacks are playful and others they are not. Sometimes they don't breach at all.
Surfing -- Soft top surf boards can give a nasty rash on all of the uncovered areas of the body.
Fish/snorkeling/ocean -- There are shallow, mid and deep zones where different fish gather. There are some fish that look different as juveniles so that their parents won't fight with them for territory. Fewer people die each year from shark attacks in Hawaii than from coconuts dropping on their heads.