That Oceanic is an H20 Audio case. It holds an iRiver MP3 player iirc. I have an H20 Aduio case for my Nano, but it is a swimming case that only goes to 10ft. I believe that case linked above is the only deep water case they make. But you might be able to buy H20's new earphones to use in that case, but that might cause problems. The new earphones work kind of like ear plugs, not good for diving.
H2O Audio -- Waterproof Your iPod
So maybe an iPod case attached to your float and remove the ear buds before your descent?
Good luck.
