[MV=PY]

"I think it might be the result of the right angle of light through the bow spray."

I think you might be right. It looks very close.

[norwaypinesavage]

Rainbows always form an arc of a circle, or even sometimes a complete circle. The shadow of your eye, or in the case of a picture, the shadow of the camera lens, is always at the exact center of that circle. That’s why you generally will only see rainbows in the early morning or late evening, when the sun is low on the horizon.