These ultralight waterproof bags are great for lining your pack or perfect for wrapping you backpack when its deck mounted on your raft. Keeping all the straps secure and reducing any chance of entrapment. Also giving an extra layer of water protection to your gear too.
See the pictures for some Open Water bag mounting options...
Here's what Exped have to say about these:
Ultralight, waterproof pack liner with roll-top closure made of 15 D rip-stop nylon with silicone coating on the outside and PU coating on the inside. Fully taped seams and a lightweight version of the closure and buckle. The translucent fabric allows you to recognize the contents. The slippery silicone coating ensures easy removal of the liner from the pack. The Packliner UL keeps contents dry and the bright colors ensure good overview.