I downloaded a file (dehavilland.zip, FSX props, page 4) from Simviation and have a couple issues with it.
First, I can't get the plane to stop moving forward after landing on the water unless I stop the engine.
Second, the plane keeps hopping out of the water.
Any ideas as to what would need to be tweaked?
Well, some of that may be pilot error.

You hop out of the water on landing, right? If so, then slow down quite a bit before committing to your approach.
It is actually common practice from what I have read to shut down your engine when landing a float plane. If that doesn't work, then either engage reverse thrust, OR do it the "turbo" way, drop your propeller pitch to 0, and push the throttle to full.
