There's nothing like salt water or fish slime to glop up your sunglasses. Once that stuff gets on there, it's difficult to remove; a cloth just seems to smear it around and make it worse than it was.
Solution: We've discovered Flents Wipe 'N Clear anti-fog/anti-static, pre-moistened lens cleaning tissues. Available at Target and other stores, these wipes do the job: they remove glop and smears and they air-dry so there’s no need to carry a separate drying cloth. Works on glass and plastic lenses and will not scratch them.
TIP: Keep a couple of them tucked up inside the lining of your fishing hat.