Sure, staying out of the water is an obvious piece of advice, but it's one that characters in films like these never seem to follow. Like remaining in a group in a horror movie, staying out of the water in a piranha film is a vitally important piece of advice and one that individuals reject to their detriment.
In real life, staying out of the water is one easy way to prevent yourself from being attacked from a piranha.In Piranha 3DD, youngsters are attacked on water slides, in a lake and in pools. These attacks could have been prevented if these people chose to stay in the sun rather than going in the water. Of course, people inland aren't always safe-- see the movie for details-- but staying out of the water is a good first step for surviving.