Bioluminescent

My wife and niece reported seeing luminescence when they dragged their feet on the wet sand on Humarock Beach (Cape Cod Bay). I went down the following night and saw tiny glowing green lights when I stomped on the wet sand near the water. They would stay on for just a few seconds.

Several days later we saw similar lights on the South River, but these lights were in strings ranging from 1/4" to several inches long, and some were connected in groups like lines of longitude on a map. These lights responded to footsteps--no stomping required--and stayed on for several seconds.