The question of whether breast implants float in water is a common curiosity rooted in material science. The answer depends entirely on the physical properties of the materials used in the implant and how those materials interact with the water surrounding them. Exploring this topic requires an understanding of basic physics, specifically the concept of buoyancy, which governs why any object sinks or floats. This exploration provides a clear, scientifically grounded explanation of the different behaviors of the two main types of breast implants when submerged.
The Physics of Why Things Float
The determination of whether an object floats or sinks is governed by the principle of buoyancy, first described by Archimedes. This principle states that any object wholly or partially immersed in a fluid is acted upon by an upward buoyant force equal to the weight of the fluid displaced by the object. If the buoyant force is greater than the object’s weight, the object floats.
The relationship between an object’s mass and its volume, known as density, is the practical measure used to predict this behavior. Density is typically expressed in units of mass per unit volume, such as grams per cubic centimeter (g/cm³). The density of the surrounding liquid serves as the benchmark for comparison.
For pure water, the density is approximately 1.0 g/cm³. An object with a density less than 1.0 g/cm³ will float. Conversely, an object with a density greater than 1.0 g/cm³ will sink because its weight exceeds the buoyant force of the displaced water. This simple comparison of densities is the foundation for predicting the behavior of breast implants in water.
How Implant Filling Affects Buoyancy
The material inside the implant shell is the primary factor determining its overall density and, therefore, its behavior in water. Implants are generally filled with either a sterile saline solution or a cohesive silicone gel. The density of the filling material relative to water provides the direct answer to the question of floating or sinking.
Saline-filled implants contain a sterile salt-and-water solution, which is similar to the fluids naturally found in the human body. This 0.9% medical saline solution has a density of approximately 1.0046 g/cm³ at body temperature. Because this value is extremely close to the density of water, a saline implant is considered nearly neutrally buoyant and would sink very slowly, if at all, in fresh water.
In contrast, silicone-filled implants contain a highly cohesive, medical-grade silicone gel. This gel is manufactured to be denser than water, with measured densities typically ranging from 1.02 to over 1.07 g/cm³. The higher density means that silicone implants definitively sink when placed in water.
The outer shell, typically made of a thin, solid silicone elastomer, contributes to the overall weight and volume of both implant types. However, the density of the large volume of filling material is the dominant physical characteristic that dictates the implant’s buoyant properties.
Real World Impact of Implant Density
While material science indicates that silicone implants sink and saline implants are nearly neutrally buoyant, this difference has almost no practical consequence for the wearer during daily activities. The implants are surgically integrated into the body, which itself is a complex system of varying densities. The average density of the human body is only slightly less than water, which is why most people can float with minimal effort.
The presence of the implants does not significantly change the overall buoyancy of the person. The mass of the body and the volume of air in the lungs are the factors that most influence a person’s ability to float or swim. The small difference in density between the two implant types is functionally negligible when considering the total body mass.
Furthermore, concerns about the effects of pressure changes, such as during deep-sea diving, are related to the implant shell’s strength and the compressibility of the filling, not buoyancy.