Water dumbbells are exercise tools designed for aquatic workouts. They are typically made of foam or plastic and filled with water, providing resistance during exercises. These dumbbells are lightweight when dry but become more challenging to lift when submerged, making them ideal for strength training in a pool. Using water dumbbells can enhance workouts by engaging various muscle groups while minimizing impact on joints. They are popular in aqua aerobics and rehabilitation programs, allowing users to improve strength, endurance, and flexibility in a low-impact environment.