Smells like low tide.
Well I bring a throw bag on just about any trip, flat water or otherwise and just use it for my boat rope. I like Jans, sturdy bags and reasonable price. If you can't get good at throwing a regular throw bag with a few practice throws, you might want to rethink being a boater
I might get a throw bag for river floats. I've thrown one before, and I agree it takes a few practice throws to get the hang of it.