The most common image of hydrotherapy is doing exercises in a swimming pool but there are other types of treatments that can be used as well.

Hydrotherapy is the use of water to treat disease or illness and has been around since ancient times.

Many conditions are treated, at least in part, with hydrotherapy. The condition or disease determines the type of therapy used.

Using a swimming pool for gentle exercise, stretching sessions and physiotherapy are often used as a form of treatment.

At Worthing Hospital the sessions have become so popular, physiotherapy staff have set up a programme of extra courses aimed at building on the exercise programme offered on the NHS.

Patients are charged £28 for four sessions and the profit will be used to buy new equipment for the pool.

This type of activity is ideal for people with muscular and joint injuries as weight is supported by the water so there is less stress and strain put on the body.

More than 100 patients a week benefit from the service on the NHS, each receiving six sessions of treatment.

Senior physiotherapist, Anne Jackson said: "Many of our patients were wanting to continue the classes and were willing to pay for the extra sessions so we are delighted we have been able to extend the arrangements.

"Aquafit is an ideal way for patients to take control of their own health and fitness."

Patient Audrey Kelcey, who recently had a hip replacement operation and suffers from arthritis of the spine, said: "Coming here every week has made me more flexible and I really notice if I miss a class."

Aquafit sessions are taking place at swimming pools across Sussex and organisers say it is a perfect way for people to get fit, meet new people and have some fun at the same time.

The sessions can be strenuous but being in the water means not so much strain is put on the body as during aerobics sessions in the gym.

Hydrotherapy has been used for wound care, to increase blood flow and improve circulation, for relaxation and to reduce anxiety.

A whirlpool may be used as part of the treatment for certain types of wounds. It can help reduce inflammation by increasing blood flow to the wound.

Other benefits include cleansing of the wound and relieving pain.

Typical treatment includes placing the person in a warm whirlpool once or twice a day for 20 minutes.

The wound is rinsed with clean water afterwards. The steam baths and saunas commonly found in spas or gyms are usually not used medically.

However, they are often used to make people feel better or for treating muscle strains. Most experts advise people not to spend more than 15 to 20 minutes in either a steam bath or sauna.

Neither is advised for pregnant women, people with infections, lung or heart diseases or circulation or blood vessel problems.

An immersion bath is used to relieve back pain, sore muscles and body aches due to flu or colds.

The bath also promotes relaxation and helps to relieve mild anxiety. Water is kept at body temperature or a little warmer.

People with heart problems, circulation problems, numbness or varicose veins should check with a medical expert before using this therapy.

After therapy, people can usually return to normal activities or their room if in the hospital.

Many people who use whirlpools or a warm immersion bath report a feeling of relaxation and calm.

People who use cool baths for relief from itching, heat, or swelling often report a reduction in symptoms.

More details about aquafit sessions are available from local swimming pools and leisure centres.