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Do Tennis Balls Float?


Tennis balls, a common sight on courts around the world, serve more purposes than just sports. People often use them in various physical activities and even as toys for pets. But have you ever wondered if these ubiquitous green spheres can float on water? This article dives deep into the buoyancy of tennis balls and what factors influence their ability to stay afloat.

What Are Tennis Balls Made Of?

Tennis balls are constructed from a hollow rubber core covered in a wool or nylon felt. The rubber is designed to be lightweight yet durable, providing the necessary bounce required by the sport. This construction is crucial as it directly impacts the tennis ball's density, an essential factor for buoyancy.

Properties of Tennis Balls

The density of a tennis ball is slightly lower than that of water, which is why it can float. The felt covering, while hydrophobic (water-repelling) at first, can absorb water over time, which might affect its buoyancy. Furthermore, the air pressure inside the ball helps it maintain its shape and contributes to its ability to float.

Why the Question of Buoyancy?

Understanding whether tennis balls can float is useful for players and coaches who frequently retrieve balls from water bodies near courts. It’s also essential for dog owners and trainers who use these balls as toys in pools or lakes.

Experiments on Tennis Ball Buoyancy

To test if a tennis ball floats, you can perform a simple experiment: Place a tennis ball in a container filled with water. Observe whether the ball stays submerged or rises to the surface. Typically, a new tennis ball will float, although not entirely above the water line.

Factors Affecting the Buoyancy of Tennis Balls

Several factors can affect how well a tennis ball floats:

  • Water Absorption: Over time, the felt can absorb water, increasing the ball’s weight and decreasing its buoyancy.
  • Wear and Tear: A worn-out ball may have cracks that allow water to seep into the rubber core, further affecting its flotation.
  • Air Pressure: Tennis balls lose air pressure over time, which can affect their structural integrity and buoyancy.

Practical Applications

Floating tennis balls have practical uses in water sports and activities. They are often used for games and training exercises in pools. Dog trainers also use floating tennis balls for fetch games in water, helping dogs get comfortable with swimming.

Safety and Considerations

When using tennis balls in water, ensure they are clean and free from wear that could lead to water absorption. It’s also crucial to consider that not all dogs are natural swimmers; always supervise pets during water play.

Environmental Impact

Consider the environmental impact of using tennis balls in natural water bodies. Materials from worn-out balls can be harmful to aquatic life. Opting for eco-friendly balls or those specifically designed for water use can be a responsible choice.


Tennis balls do float, but their ability to do so can be influenced by various factors including wear, water absorption, and loss of air pressure. Whether used in sports or play, understanding these factors helps maximize their safe and effective use in water environments.


  1. Do all tennis balls float the same way?

    • No, the buoyancy can vary depending on the ball’s condition and how waterlogged it gets.
  2. Can tennis balls be used safely in swimming pools?

    • Yes, but it’s best to use newer balls to avoid water absorption and ensure they float well.
  3. Are there special tennis balls for water use?

    • Yes, some balls are designed specifically for water play, often with extra buoyant materials.
  4. How long will a tennis ball float before sinking?

    • This largely depends on the condition of the ball; a new ball can float for a very long time unless it's damaged.
  5. Is it safe for all dogs to play with tennis balls in water?

    • Dogs should always be supervised, especially if they aren't experienced swimmers, to ensure safety during water play.