Background: Balance dysfunction (BD) in Parkinson's disease (PD) is a disabling sign leading to falls which have a negative impact on the quality of life. It is known that aquatic therapy could be useful to train balance given its physical features and for reducing patients' fear of falls. Many studies have evaluated the efficacy of land-based physiotherapy in treatment of BD, but few studies have investigated the efficacy of aquatic therapy on balance and none of those assessed clinical measurements in a clinically, relevant follow-up period.