Ok I an not familiar with your camera, (I will try to get a look at the spec sheet later) There are a few things toy can try even with f8. Yes you are right high f number = smaller aperture. 1. Doing the water shots in low light, early morning or late afternoon/early evening when the light is dropping off will help. 2. Getting a polarizer or Neutral density filter for your camera (if available) will reduce the light through the lens. The shutter speed you need is somewhere between sec-4 sec depending on the velocity of the water flow, if the wafer flow is very fast even 1/15 may be slow enough.

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