This thing is like what mermaids need
So if were a mermaid and I've never been one so this is all speculative - I'd buy one. When I got to land and needed to float to watch handsome beach-princes toss frisbees to dogs and blast gulls with bread crumbs I'd inflate the pack and use it as a flotation device.
Then when I needed to dive back my village I would deflate all air, and put my electronics in the main compartment, diving to 20,000 leagues - with a dry digital camera the whole time.
But I am not a mermaid and at this point it looks like I'll never become one (which sucks) so I will just use this bag for canyoneering and keeping beer dry in the rain.