Good question! A 100% waterproof case like the aquapack is a good way to go. Actually a cell phone is good insurane against emergency situations provided you have coverage.
I have recently gone bluetooth, which let's me answer calls using the button on the earpiece. Dialing is still done from the phone, but like you I don't do that often. So if I swim I lose just the earpiece.
However I do have the $5 insurance, the only problem with that is the inconvenience time while you wait for the replacement.
In certain areas the risk of water damage is low, others it's high. Play it accordingly.
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