After giving this photo some thourough examination, I can arrive at a few conclusions.
First, the funky line that streaks through the lower 1/3rd of the image appears to be a slightly out of focus cable or something...it may have just been on the inside border of the depth of field, and did not get entirely blurred away.
As for the "grid", I can't say anything definitively. Here are some facts that I see about it:
- It only exists within a very specific area of the water...only in the area with the boats.
- It has a VERY specific size, structure, and shape unfettered by any measurable degree of randomness.
- It does not seem to appear on any non-water part of the photograph.
Some thoughts that come to mind are the following:
- Its actually something real..."design" of part of the bay there. Something under the surface of the water that was picked up by your exposure.
- Could be tested by just looking at the same scene with your own eyes and see if the grid pattern is visible without the camera.
- It is the result of something closer to your camera, outside of the bounds of your depth of field, that has been blurred just enough to be nearly invisible, but visible enough that it affected the lower portion of your photo.
- Might be possible, however outside of the slightly blurred cable through the lower part of the scene, I can see nothing else that might hold up such a mesh or grid only in the lower part of your scene, and not in the upper parts.
- It is the result of an odd wave-interference pattern in the water itself.
- Rather unlikely, given that such a clear and regular interference pattern would require a rather specific underlying waveform to occur...and the waves on the water otherwise look quite random.