It's probably just the areas of shallow water, while the deeper water appears dark blue. You notice the "ecto" color is only around the jetty and extends outwards from there. Same with the jetty in the way background. Or it could be lighter color due to a rip churning up sand as it moves...
Allenhurst Beach Club has an annual "Dying of the Ocean Day" every summer. It has been a tradition for a number of years now. They dump some kind of green dye in the water and all the kids go swim around in it.
