First off, the cold will help take out heat and inflammation, the water temperature stays at 36 degrees for the entire treatment but can be adjusted as necessary. Secondly it helps control enzyme deterioration on tendon and ligaments in the early stages of an injury, thirdly it massively increases circulation. When horses are in the spa they under go vascular constriction, but when they are lead out of the spa blood will rush to the cooled area to to warm it, bringing oxygen and healing nutrients to it in the process.
The spa has a high level of both Epsom Salts (MgSO4) and ordinary Salt (NaCl). Salt water has been known to be therapeutic for years. People use to be sent to the seaside for a wide range of ailments, from open wounds to arthritis. It has a poultice effect as well as an endothermic draw which will further increase the temperatures effect.
The spa is also aerated. This increases the dissolved oxygen content of the water as well as providing a massage effect. The fact that the water is continuously moving also means that the contact surface is also constantly changing.
The water can be adjusted to any depth you require.