I have seen people actually build sand boxes and shoot at high angles to give a beach effect in the studio or use props in the background and control dof to appear more beach worthy.
Of course you can get "Fashion" with more dramatic lighting and pose with your model on white seamless and be ok. You just don't want it to look like another, "i just want to get a girl half naked in my studio and shoot pictures."
I think pattern swimsuits in the studio can give off that cheesy studio feel to so try and keep your swimsuits, solid color.
A quick idea would be to mock up a grass hut or something tropical without being cheesy and control it with light and dof. For instance, shoot your light through a pattern to create an appearance of scattered natural light and place the model accordingly to please the light on the model. Use gels to warm the scene and various light modifiers to give more dimension in lighting to help.
A good idea would be to build a set and practice with the scene before the model comes into the studio.
Outside of that....bring a truck load of sand and tiki torch your studio....