The rainbow hugs the water because the sun was about 40° high. A rainbow's centre is always directly opposite the sun. As the sun rises the rainbow falls. Its radius is about 42° and when the sun is 40-42° high only the extreme rainbow top is above the horizon.

The requirement that the sun be lower than ~42° limits rainbow visibility. Rainbows rarer than we think and halos are visible more often. Rainbows are seen only a few times each year unless you live in the 'rainbow centres' of Hawaii, Ireland and Western Scotland.