Hydrotherapy:
'Hydrotherapy involves the use of water for pain-relief and treating illness. The term hydrotherapy itself is a water cure as it was originally marketed by practitioners and promoters in the 19th century. It's the generic term for water therapies using jets, underwater massage and mineral baths cold plunge and others. These treatments use physical water properties, such as temperature and pressure, for therapeutic purposes, to stimulate blood circulation and treat the symptoms of certain diseases'... 'When you are in pain or under stress, chemical changes in your body can cause the blood pressure and pulse rate to increase, Having regular hydrotherapy treatments can help you to reduce these symptoms by relieving swollen joints and slowing down the process of stress reaction. This will help you to relax and unwind, which is easier for you, helping you to deal with your pain'

Occupational Therapy:
'Occupational therapists work with individuals, families, groups, communities and organizations to facilitate health, well-being and justice through engagement in occupation. "Occupational therapy is as a profession concerned with promoting health and well being through occupation. The primary goal of occupational therapy is to enable people to participate in the activities of everyday life. Occupational therapists achieve this outcome by enabling people to do things that will enhance their ability to participate or by modifying the environment to better support participation" - The World Federation of Occupational Therapists
Occupational therapists use careful analysis of physical, environmental, psychosocial, mental, spiritual, political and cultural factors to identify barriers to occupation.'

Found on http://www.wikipedia.org/ and www.hydrotherapy.org.uk