Buoyancy in Freediving

Weight in water: optimizing buoyancy for energy savings in freediving

Freediving is a sport that requires not only physical preparation and the ability to control one's breathing, but also an understanding of scientific principles, particularly physics. An object is positively buoyant when the body naturally floats to the surface, which occurs due to the buoyant (Archimedean) force being greater than the weight of the body in water.

According to Archimedes' principle, any body submerged in a fluid experiences an upward force equal to the weight of the fluid that is displaced by the body.

To define positive buoyancy of an object, it is sufficient to ensure that the object does not sink but remains on the surface of the water. Conversely, negative buoyancy occurs when a body is heavier than the water it is in, causing it to sink.

In this context, it is important to understand that a body under water is subject to various forces: the force of gravity applied to the body, and the buoyant force acting on the submerged volume. According to Archimedes' principle, these forces determine whether a body will float, sink, or remain suspended. Managing these forces requires knowledge and experience from freedivers, allowing them to optimize underwater movement and minimize oxygen consumption.

In the realm of freediving, buoyancy effect is instrumental because it influences the conservation of a diver's energy reserves. By skillfully managing buoyancy, a freediver can optimize their movements in water, thereby minimizing effort and maximizing the efficiency of their dives. This conservation of energy, which could be referred to as "buoyancy free energy," is particularly significant as a diver descends or ascends, where the volume of trapped air in their lungs and wetsuit compresses or expands due to varying water pressure. While the average freediving depth can differ widely between novices and experts, the principle of buoyancy control remains critical for all levels.

How much weight for freediving?

The neutral buoyancy zone in freediving is the depth at which the freediver stops floating and does not yet begin to sink. At this depth, the force of gravity equals the lifting force created by the water. The start of this zone depends on several factors:

  • Wetsuit thickness: A thicker wetsuit provides more buoyant force due to the foamed neoprene capturing air during material production. Consequently, with a thicker suit, the neutral zone starts at a greater depth because more water is needed to compress the neoprene.
  • Amount of weights: Increasing the amount of achieves the neutral zone at a shallower depth, as the additional weight helps overcome the buoyancy of the wetsuit and air in the lungs.
  • Volume of air in the lungs: Freedivers usually take a full breath before diving to increase their air reserve. A larger volume of air in the lungs increases overall buoyancy, shifting the neutral zone to a greater depth. As you dive deeper, the air volume decreases due to increased pressure, and the buoyant force decreases.

Practical tips for freedivers

  • Use of a weight belt: Start with less kg and gradually increase it until the desired level of the neutral zone is reached. For recreational freediving, this is usually at a depth of about 10 meters.
  • Buoyancy check: To test, you should take a vertical position in the water and fully exhale. Ideally, the waterline should be at the level of your eyes. If your body starts to sink under the water, you should immediately return to the surface and adjust the amount of the weights on the belt by removing excess kilograms.
  • Training and practice: Practice freediving techniques with an experienced instructor to find the most effective methods for your body and freediving discipline.


Understanding how does buoyancy change with depth is a cornerstone of safety and performance in freediving, which every serious practitioner aspires to perfect throughout their sports career. Successful regulation requires knowledge of your body and equipment, as well as the ability to adapt to changing underwater conditions such as water salinity and diving depth.

Experienced freedivers often perform tests before diving to determine how much weight they need and at what level they will reach the neutral zone. This may include testing at the surface and at the expected neutral zone depth.

Ultimately, mastery in buoyancy management is a cornerstone of safety and performance in freediving, which every serious practitioner aspires to perfect throughout their sports career.

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