1. Find a good shower. You might have to rent a room somewhere. Or, for the most flexibility in executing your creative vision: make your own with some tileboard from the hardware store and some and 2x4s. Set it up outside, in the driveway or parking lot or backyard, and attach your shower head to the end of a hose.
2. Figure out how you want it to be lit. If you don't have the gear for it, rent it. If it's outdoors during the day, you'll likely want a scrim to eliminate the hard shadows from direct sun.
3. Find a model who doesn't mind ruining a suit. Or get a suit from a thrift shop, and find a model who fits it.
4. If your shower is outdoors (e.g. the beach) figure out how you want the background to appear. Blurred, obscured, etc. Also, if your shower is outdoors, figure out what time of day is most appropriate for your shoot (hint: it's probably about an hour before sunset).
5. Practice! Practice well in advance, so the day of the shoot you are 100% confident in how it will go down.
5a. First practice without a model, see how the light and the camera capture the water flowing out of the shower. Play around in your own shower at home, if you must. Experiment with different settings. If you're using flash, experiment with different combinations of shutter speeds and flash powers. A long shutter speed and a second-curtain-sync flash might be cool.
5b. Then practice with with a model (doesn't have to be the real model in a suit yet, just a buddy who doesn't mind standing in the shower while you practice and experiment). See how the water and camera settings and lights all work together to make the image. Continue adjusting settings as needed.
