Also -- pick up or rent a copy of the video "Whitewater Self defense". It's a nice review of some basic white water safety.
Also.. some things to think about if you are a swimmer...
First -- the best is to avoid being a swimmer, learn how to avoid getting flipped (river reading, braces), learn how to roll.
If you do swim, you are more important then any gear that is floating around. If there is any chance that holding onto gear is going to put you into more danger, then let the gear go.
If you can do so safely, hold onto your paddle, or at least try to toss it into an eddy, onto the shore, or towards a group of paddlers (just remember that the other paddlers should be watching you more then the equipment).
If you can do so safely, also hold onto your boat, you might even find that it can help in a very long swim, you can use your boat as a boogie board (especially since you do have floatation in the boat right?), or as a "bumber" -- just make sure that you do not get trapped between a rock and the boat