Rob,
I have the Optio 10. I call it my point and hope because it does lack a viewfinder like most point and shoots. On the positive side you can get pictures where no SLR dares to go. It takes a good picture but has all the limits of a point and shoot (slow to respond, limited control, no viewfinder,) and the positives (small, easy, light). You will never publish a picture from it but it works fine for web quality images.

To clean it in salt water just rinse it with fresh water, shake it, and dry the lens with a lens cloth if needed. It is waterproof but a splash bag will keep the lens from getting spotted.

I have not used the Olympus but I think it is a little better.

I recently purchased the Aquapac SLR Camera Case for my SLR. It will not fit a Pro body and a Canon 40D is tight. The barrel fits consumer grade lenses with up to a 72mm filter size but a 77 is too large. It does allow the functionality of an SLR but it is hard to see through the viewfinder. It is also bulky.
Scott