To determine if a watch is suitable for swimming or diving, consider its ATM or depth rating. Generally, a watch with a minimum rating of 5 ATM (50 meters) is suitable for swimming in shallow water, while a watch with a rating of 10 ATM (100 meters) or higher is suitable for snorkeling and water sports. For scuba diving, a diver's watch that meets the ISO 6425 standard with a minimum water resistance of 20 ATM (200 meters) is recommended.