I guess you're using a compact or bridge camera which will limit your possibilities, however it should still be possible. If f8's your limit then give it a go I focus on the spot that the drop will hit, if you back off a touch and lower your shooting angle then that should be fine. Take loads of shots and when you get a good one write down what you did (good Splog advice). Post up your results and ask lots of questions people here should be able to help. Be careful though this can get addictive
Sorry not familiar with the P90 but I doubt if it will limit you much at all if f8 is max it's probably equivalent to f16 on an SLR. Have you got an off camera flash cos that would help