Beach Rain Walk

With showers rolling through all day long, rather than be cooped up here I put on swim trunks and a T and walked down the beach impervious to rain. I had the place to myself, and the rain wasn't that bad - it's almost warm - though with the wind up can be a little tedious.

I took the Go Pro camera (in its waterproof case) and shot some burst mode of the sea (10 rapid fire frames) and reviewing them one shot picked up something I can't figure out. The wind was blowing but there's a really long streak in just one shot, too long and not the right angle to be something flying by. My best guess is a little drop of water on the case window over the camera lens hit and blew by, but I don't think that's what it is.
Here is an animation of the three frames (with before & after) at approximately speed shot (ten frames per second) in a loop. To slow it down hover the mouse over the animated image; moving left and right you can see the frames slowly. Any ideas what this is?

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Here are the three consecutive frames: