I believe you can get that effect with your Optio. If you can turn off the auto or program setting and then select the apature and shutter speed manually.
If it has a shutter priority setting, set the shutter speed slow (1/2 second or so), allow the camera to select an appropriate apature, put the camera on a tripod and use the self timer so you don't get camera shake when you press the shutter release button. It's really not difficult
One way I've done in the past with 35mm equipment is look at the field of view and mentally count how long it takes the water (or a leaf or something on the water) to move completely across the field of view of my picture. Let's say it's 2 seconds. I will then find some combination of apature and shutter speed that will allow me to get a good exposure at as close to 2 seconds as I can.
I know it's a long winded description but it should work or at least get you close enough that you can take it from here.