I’ve used Underwater Audio’s iFloatie in both the pool and ocean, for $10 it is cheap insurance against losing your waterproof iPod.
A simple, thin, form fitting rubber jacket for your Shuffle, with a tiny hole in it is core to the iFloatie kit. The jacket is just to hold the iPod with a tether to whatever you clip or tie it off to, it does not provide additional waterproofing. It does not make the unit harder to use, however the buttons are stiff already.
A branded iFloatie orange float can be threaded on to the tether and attached to the case. Now your iPod floats! In the open ocean, surfing or diving, this may be the only way to find your iPod, should it escape.
I took the orange float off the tether and simply ran the tether through my mask straps for swimming laps in a pool, I didn’t like being bopped in the head. In the ocean I clipped the iPod to my rash guard collar, under my wetsuit and let the float sit tucked in there, I had to unzip to adjust volume. For scuba diving we’ll see, prior experience with audio have been lackluster.
If you are going to take your $150 waterproof iPod in the open ocean, iFloatie may help you hold on to it.