Is water therapy a type of resistance exercise for those with RA?

The American College of Sports Medicine recommends water aerobics as a mode of cardiorespiratory training for individuals living with rheumatoid arthritis

Their recommendation for resistance training, also known as strength training is the following:

1. Circuit training
2. Free weights
3. Weight machines
4. Elastic bands
5. Isometric exercises

The ACSM recommends one or more sets of 2-3 reps initially, building to 10 repetitions 2-3 days per week.

Hope this is of help to you.

Reference:  ACSM's Exercise Management for Persons with Chronic Diseases and Disabilities - Third Edition