The first step in considering a separate tub and shower is to make sure you have enough room. Not every bath is large enough to accommodate separate fixtures, but you will be surprised at what can be done with even a modest-size bath. Using the sizes of typical fixtures, draw a scale plan of your bathroom and see what you can get to work. The design of this bath is both spacious and accessible.
Whirlpools come in comparable sizes.
Corner shower or tub units can be particularly effective space-stretchers. If your survey comes up short, don't despair. There are several ways to squeeze needed square footage out of dead space. By walling off a door and backing the bath out into the corridor, you can claim extra room. Like kitchens, bathrooms are defined not so much by what you can squeeze into the room as they are by how much space is required to make the room work.