Science of WaterSOWFoundations
The Properties
of Water
The environment is part of the program
Water changes how the body experiences gravity, drag resistance, hydrostatic pressure, and heat—creating distinct conditions for training, recovery, performance, and re-adaptation.1
Photography © Stuart Davidson
Why water feels different
The body does not experience water as a single thing. It experiences several forces at once.
Four properties shape what the body experiences during immersion.
01
Buoyancy
Changes weight-bearing and the relationship with gravity.
As immersion increases, buoyancy supports more of the body and reduces effective loading through the lower extremities. This can make selected movements more accessible while preserving the ability to move and work.12
Influenced by Depth, body position, and immersion level.
02
Drag Resistance
Turns movement itself into resistance.
Water resists motion. As speed, surface area, direction, body position, or turbulence changes, the demand placed on the body changes with it.1
Influenced by Speed, surface area, direction, body position, and turbulence.
03
Hydrostatic Pressure
Surrounds the body with pressure that increases with depth.
Immersion can influence circulation, fluid movement, and breathing mechanics. Duration determines how long the person is exposed; it does not determine the pressure itself.12
Influenced by Depth, body position, and immersion level.
04
Thermal Conductivity
Changes how quickly the body gains or loses heat.
Water temperature, exposure time, exercise intensity, and surrounding conditions shape comfort, thermal strain, readiness, and recovery conditions.12
Influenced by Temperature, exposure time, exercise intensity, and environment.
The lightbulb moment
The water can support you and resist you at the same time.
The same movement can become more accessible and more demanding because water supports the body while resisting its motion.
What this means for AquaFit Sports
The environment is not passive.
It is part of the program.
AquaFit Sports does not treat water as one fixed training setting. The same movement can become more accessible, more demanding, or serve an entirely different purpose depending on how the environment is used.
Depth
How much support and weight-bearing are appropriate?
Depth changes buoyancy, loading, hydrostatic pressure, balance, and movement control. Too deep and buoyancy can interfere with control. Too shallow and you may lose the support or unloading the movement needs.
Depth is not a benefit by itself. It is a dosage decision.
Demand
How much drag resistance and conditioning demand are intended?
The body is the first resistance tool. Speed, surface area, range of motion, body position, and turbulence change how strongly the water resists movement. Equipment at the wrists or ankles can amplify that demand when the person can control it.
Equipment does not create the principle. It amplifies it.
Direction
Where should drag resistance, balance, and stabilization come from?
Water resists movement in every direction. Reversals, cross-body patterns, and turbulence can turn a familiar movement into a very different challenge.
Purpose
What should the session accomplish?
The same aquatic environment can support strength, muscular endurance, cardiovascular conditioning, mobility, active recovery, rehabilitation or re-adaptation, and performance support.
Purpose determines what should be emphasized—and what should be restrained.Founder Field Note
Finding the sweet spot
The research explains what water’s properties do. Experience teaches you how to bring them together for the person standing in front of you.
One thing nearly two decades in the water has taught me is that more is not always better.
Take buoyancy.
When someone is too deep, buoyancy can begin making it harder for them to control the movement. When they are too shallow, you can compromise the very effect you are trying to create.
It is about finding the sweet spot.
The depth where the water provides enough support, but the person can still stay grounded, control the movement, and do the work with purpose.
That is where experience comes in.
Temperature works in a similar way.
I do not draw a line in the sand at one number. I look at the person, the water, the weather, the direct sun, the purpose of the session, and how hard I am asking them to work.
As the temperature rises, I ease up on the cardiovascular push.
That does not mean the water is no longer useful. I may still use drag resistance to create serious muscular work. I simply become more selective about how long and how hard I keep the client pushing cardiovascularly.
The warmer the water becomes, the more I watch for lethargy, slower recovery, and the body taking longer to settle.
I often ask clients to experience the difference for themselves.
After a hard effort, stay in the water and notice how long it takes your body to begin normalizing.
Then, another time, step out of the pool right away and compare the difference.
Many clients notice that they begin sweating once they leave the water. In my own training and client work, I have also repeatedly noticed heart rate—and often breathing—begin to settle more quickly when recovery continues in the pool.
The science helps explain part of what I have been seeing. Water transfers heat efficiently, and the body’s thermal response during aquatic exercise depends on water temperature, exercise intensity, and the length of exposure. Research has also found faster early heart-rate recovery under certain immersed recovery conditions.34
The breathing response is something I have observed repeatedly in clients and experienced personally. Until research tests that exact comparison, it should remain identified as my field observation rather than a universal scientific claim.
To me, this is part of the intelligence of water.
Buoyancy, drag resistance, hydrostatic pressure, and thermal conductivity do not work in isolation. They are all present at the same time.
My role is to understand how they are affecting the person in front of me—and find the combination that allows them to move, work, and recover at their best.
The goal is not to maximize any one property of water. It is to find the sweet spot where the properties work together for the person and the purpose.
Water remains the teacher.
The work is learning how to listen.
The larger lesson
Water changes the possibilities of movement.
Water does not make every exercise easier. Its value is adaptability: the same environment can reduce loading, create drag resistance, surround the body with hydrostatic pressure, and shape thermal demand.
Understanding those properties does not replace coaching. It makes better coaching possible.
“Water doesn’t just surround you. It shapes what’s possible.
”
Water is not a backdrop.
It is one of the variables that determines what the training becomes.
Sources + footnotes
Research references
- Torres-Ronda L, Schelling i del Alcázar X. The Properties of Water and Their Applications for Training. Journal of Human Kinetics. 2014;44:237–248. DOI: 10.2478/hukin-2014-0129. PMID: 25713684. PMCID: PMC4327375.
- Becker BE. Aquatic Therapy: Scientific Foundations and Clinical Rehabilitation Applications. PM&R. 2009;1(9):859–872. DOI: 10.1016/j.pmrj.2009.05.017. PMID: 19769921.
- Al Haddad H, Laursen PB, Chollet D, et al. Effect of Cold or Thermoneutral Water Immersion on Post-exercise Heart Rate Recovery and Heart Rate Variability Indices. Autonomic Neuroscience. 2010;156(1–2):111–116. DOI: 10.1016/j.autneu.2010.03.017. PMID: 20403733.
- Garzon M, Dupuy O, Bosquet L, et al. Thermoneutral Immersion Exercise Accelerates Heart Rate Recovery: A Potential Novel Training Modality. European Journal of Sport Science. 2017;17(3):310–316. DOI: 10.1080/17461391.2016.1226391. PMID: 27598988.
Cite this article
Davidson S. “The Properties of Water.” Science of Water. AquaFit Sports. Publication date and permanent URL to be added when the article is published.
Editorial standard
Published research establishes the scientific foundation. AquaFit Sports interpretation and Founder Field Notes are identified separately.