Waterproof watches are designed to resist water penetration, making them suitable for activities like swimming and diving. They are tested for water resistance, often rated in meters or atmospheres (ATM), indicating how deep they can go without damage. Common ratings include 30m, 50m, and 100m, with higher ratings suitable for more intense water exposure. These watches typically feature sealed cases, screw-down crowns, and durable materials like stainless steel or rubber. Brands like Rolex and Seiko are known for their high-quality waterproof models. It's important to note that "water-resistant" does not mean "waterproof," and regular maintenance is essential to ensure their longevity.