Why not just spend a few dollars and get a good anchor light? A good light should send all the light to the sides and none down on the boat and passengers.
If you must by out at night with no lights, follow Lakegeezer's advice, anchor in the Witches.
Seriously, it's pretty dangerous, this wan't that long ago and it could have been much worse for all involved:
http://www.winnipesaukee.com/forums/...ead.php?t=4936