It's got to be:
A bird, flying left ot right. The streak is because the darkness caused the camera to use a long exposure time. The swervy parts are the wings, and the motion of the central brighter blur (which would be the bird's body) even veers up a little while the wings come down.
Also, at the bottom of the wings' strokes, you can make out two distinct streaks that, given their angle and relation to each other, appear to be the tips of each wing: one closer to the camera, the other on the far side.
As to why it's glowing like that, I'm less sure. My best guess is...
that there's a constant light source off to the right, possibly behind or above the camera, which is lighting up the sand nearby, and also lights up the bird. It's not the camera's flash because the shadows shoot off to the left, and cameras don't usually use flashes in conjunction with a long enough exposure to create that long of a streak.
It would need to be a smallish, light colored bird, probably moving very quickly across the frame. I deduce this from multiple data points: the length of the streak is way way longer than any blur made by the waves, so it has to be moving quickly. Also, to be that bright, it needs to be fully inside the bubble of light created by the light source, and that bubble only appears to go out 20-30 feet on the sand. The closer it is to the camera, the slower it could move, but if we get it down to insect size, like a moth, each wing beat would have more of an effect on the altitude than what we see.
So, yeah, it's got to be a white bird flying quickly across the frame, between 10 and 30 feet away from the camera.