Showering with dexcom

My SO only showers twice a month (don't get me started), but his latest excuse is blaming his dexcom saying it comes off if he showers. We've tried various patches that go over it and they all start to peel off within a few days even without him showering. I want his blood sugars tracked but I'm also tired of having to dodge whenever he lifts his arms. Please help with advice and recommendations.