I've shot long exposures on a point and shoot that can only go to F/8 as well, although limiting there are possibilities. With an overcast day early in the morning or late in the evening will give you minimal yet usable amounts of light. If you have a *fast* flowing stream rather than a calm one it won't take as long to blur the water properly. And the final solution that others have mentioned is get yourself a neutral density filter, something like this: [link] (I haven't used Tiffen filters and cannot speak to their quality) To which millimeter size you want, either get the smallest you can get away with (measure the diameter across the front of your lens) because that will be cheapest. Or keep in mind if you ever want to get a dSLR with that you may want to get a size that will fit your lenses in the feature should you choose to upgrade. Hope this helps Hope you get some silky smooth water shots soon!
The available apertures are F3.4, F3.5, F4.0, F4.5, F5.0, F5.6, F6.3, F7.1, F8.0 see page 67 in the english handbook.
The reason for that is that there is a relation between sensorsize and the maximal usable aperture typical values are Aperture 16-22 for 135mm Aperture 11-13 for APS.-C the relativ small sensor 1/2,3 inch would give you very blurred and unsharp pictures with aperture beyond 8.
This 8 will be nearly the same as an 16-22 at the 135mm format, so you get all of the Depth of field that is possible
The only way if there is to much light is to use a lower ISO-Value ora a a grey filter (i. e. Cokin )