You'd be surprised, I didn't notice any significant reduction in air time per battery, neither handling in the wind. Granted I don't fly in extremely bad weather, but in conditions shown in the video it was fine. An I am not forgetting about spray and waves, this is handle for hand launch and (as mentioned in photo album) life-jacket. It's not designed for landing on the water but to keep drone from drowning in case something wrong happens. I did design and tested float setup that allowed water landing but that one had issues with handling due to floats being significantly lower and was rejected.
Thanks, that is my own design and construction.
Floats foam is repurposed pool noodle, plastic parts are made using 3d printer. While I already build few of those and could make one more, shipping it to you would be very expensive, I am in Europe and my guess is that you are from US like most of the forum members.
But if you have access to 3d Printer, or know someone who have, and don't mind some DIY, I could provide files and instructions for the assembly.