There are a number of devices that may prove helpful to you.
The first is an adjustable handheld showerhead with a single control faucet. This will allow you to hold the showerhead and to control the direction of the water.
You may want to install a seat in the tub area. When choosing a seat, make certain you purchase one that uses a clamping device to secure it to the tub. The clamps should attach firmly so that the seat will not move while in use but release easily so that the seat may be removed if necessary.
Finally, you may wish to install grab bars to assist your parent in getting in and out of the tub area safely.
For more information, visit the eXtension article on Bathroom Safety and Design.
