You have a choice with the D80 - either the MC-DC1 remote cord or the ML-L3 infra red remote, either will do the job you want it to (release the shutter without touching it) although the ML-L3 works best from in front of the camera (the sensor is just above the D80 badge IIRC).
Personally, to achieve slow shutter speeds, I use S mode and let the camera chose the aperture - whichever mode you use, keep the ISO as low as possible - IIRC, the D80 goes down to ISO 100. Chose the shutter speed (for exposures of 1 second and above, you want to see 1" (or more) in the display - if you see 2 rather than 2", you'll be shooting at 1/2 a second rather than 2 seconds; you'll still get milky water but the longer the exposure, the milkier it'll look.
I would suggest that you take a few shots at a range of speeds to see which speed gives you the result that pleases you. Sometimes the water can look too milky.
If the weather is too bright and you can't get slow shutter speeds even with very small apertures, you may need a Neutral Density (ND) filter which will cut the amount of light that hits the sensor. If you have a polarising filter, that can be used to both cut the amount of reflection from the water's surface and to increase the exposure time a bit.