Just for comfort and safty, here's some ideas. They can also be helpful for sex.

If you have, like someone mentioned earlier, a tub/shower combination - get a "Tub Safety Handle" (google it) - they are easy to attach to the side of the tub and very strong - I've got one. You can also get various blow-up pillows for the bathtub. I just bought a mat, with sort-of "bubbles", for the tub that prevents slipping. It's also comfotable to sit on for a bath (or whatever).