Preventing flash from messing up the lighting?

I really want to be able to take photographs in some dark places under cut banks and such in my northern Wisconsin streams. But when I've tried flash photos, I get this sort of "snowy" effect from the flash illuminating every little impurity in the water, and my photos for the most part are useless.

http://www.troutnut.com/underwater/other/s...e_2_26_04_1.jpg

(I've got some other neat photos of all sorts on troutnut.com taken under easier lighting, by the way--check it out!)

Does anyone have recommendations for effective low-budget lighting in water where tiny debris makes the flash an impossibility? I'd really like to resolve this problem... thanks!

Or, is there anything I should know about setting my camera (Olympus C-740UZ) in a way that'll let flash photos work underwater?

The bottom line is do not light the water between the camera and your subject. You will probably need an external strobe to do this. To hold your strobe either get a flexible arm system or hand hold the strobe.