There have been past threads on this, one not too long ago, so I didn't read all the posts. Everyone has a solution to a problem I consider unsolvable. I hide my key under a rock here in NS and in a metal box in the wheel well when in NY area (make sure no one is watching, IF that's possible).
I would never take any chip key into water. Period. I've LOST two of these f(&^%$g things and am out over $500US as a result (FOUND the 2nd one I lost and got no refund from Chrysler for the $260US copy they made for me, because they "Can't delete the programming--it's yours forever, now you have THREE keys"...)
Need the good old metal key and the 5 copies you get made for $1.50 each at the hardware store. And oh, you can take a copy with you on a dive--without any compartment to keep it dry.