My sunglasses are prescription and were over $500 bucks so I'm very careful with them.
Before I needed glasses I always bought the nice ones but after losing a half dozen of em over the side of the boat I just bought cheap ones to take on the boat.
I hated wearing a leash on em because you constantly sweat on em or get sunscreen on em.
I tried the auto inflating devices that go off when they get wet but try keeping a pair of glasses dry all the time.
Reminds me of my buddies auto inflate wade life vest that worked the same way. He sure was proud of em.
Until he waded into knee deep water to take a shit and rolled backwards into the water and his vest inflated.
I never laughed so hard in my life watching him flounder around trying to get his feet under him with his shorts around his ankles.
He then went and bought the one I use that has a rip cord.