One of a kind product?
Dry bag/compression sack/day sack. If there exists another product combining all of these functions I am unaware of it.
I've got a nice little OR compression dry bag that packs real small into an internal pouch. Problem? No shoulder straps. Ditto on the compression sacks I have -- great for stuffing gear, but none of them shoulder straps.
(And of course I've had plenty of regular day packs over the years, but none of them are dry bags!)
So yeah, great combination of functionalities. So far it's treated me well.
DISCLAIMER: I have not taken this on the river yet and cannot vouch for it's dry-ness. Hence the 4/5 stars.