MED-EL announced that WaterWear covers for the OPUS 2 and SONNET processors will be available late summer 2016 in the United States. Note that Zinc-Air batteries do not work in an airtight environment, so most likely 675 LR44 button cells will need to be used in conjunction with WaterWear.
In related news, MED-EL also received FDA approval for a rechargeable battery for the SONNET processor, which may work in conjunction with the WaterWear, making 675 LR44 batteries unnecessary. Also, a Mini Battery Pack and Cable have been approved for the SONNET, which may be an off-ear power solution unrelated to WaterWear.