By definition, hydrotherapy is the application of water for the treatment of physical or psychological dysfunction. Hydrotherapy or aquatics is the use of water or an aquatic environment to help with the advancement of a rehabilitation program. The use of hydrotherapy began in ancient Greece with the use of warm water springs.

When hydrotherapy is administered, a physical therapist will perform the treatment with you in the desired depth of water. The depth will depend on the activity that you will be performing, your tolerance to the water, and the amount of body weight to be unloaded. The entire treatment will be performed in the water.  Overall, the treatment will include activities that unload the spine, strengthen the muscles, and increase range of motion for the joints. All activities performed will be based on your tolerance and ability to perform the activity.

When using hydrotherapy, you can expect to have decreased weight bearing on joints with increased resistance and increased motion. Afterwards you’ll be able to move easier and with fewer symptoms, while at the same time providing greater resistance. While being in the water, your body will have increased circulation with increased cardiac output, which will lead to an overall decreased heart rate, decreased blood pressure, and increased cardiac efficiency. There will also be an increase in lung capacity with fewer issues with exercise-induced asthma. You will also find that you have increased kidney and renal function from the increased pressure and blood flow. This increased kidney function will help to decrease edema and help reduce hypertension. That last benefit is that hydrotherapy has a psychological effect of making you feel relaxed if using warm water or feel invigorated or energized with cold water. The warm water provides a calming environment while cool water will help facilitate more active exercise.

Learn more at https://www.spine.org/KnowYourBack/Treatments/Nonsurgical-Treatments/Hydrotherapy

https://www.verywellhealth.com/different-types-of-hydrotherapy-89993