الوضعية الكلبية الضفدعية

This would work well with her holding something like the side of the tub. A little more stability while maintaining the stance.

My wife is fairly small(5'4''), quite strong and athletic so this position gives her the freedom to move her hips at will as I just hold on for the ride. Her orgasms get extremely intense and the PC muscles can be like a clenched fist on my dick.
She can be very stimulated by the visual and says she really gets turned on by lowering her head, looking up between her legs and watching her hips move while both feeling and watching my shaft in her and my balls hanging below her crotch. Sometimes she also puts a hand mirror on the floor under her so that she can get a different view. I think it is really sexy to watch her as she gets herself off on watching what she is doing to me.