3x3 bit small, you shoud try draw a 3x3 box stand inside. Adding basket for shampoo or soap, your space really limited. Not impossible to take bath just small.

Your shower screen is cloths? or hard type with door? If door it got to open outward, but than open outward water may flow out.

how come water flow out?i tot shower screen is to keep water flow confined to a certain area?
yeah 3 by 3 is quite small,maybe 4 by 4?but oso depends on the shape of the shower screen u choose (ie diammond shaped,curved,square/rectangular)..dooor opening wise got sliding door,swing door or bifold door..

3ft, how you want to put in sliding? Mine 5+ft using sliding feel it tight fit. If you have baby, plan to have need to consider the baby bathtub to put inside.

Sometime if too small better don't divide it, let everything open, much better.