It looks like there was a tide going out! It must have been water flowing back after being piled up by the wind.
The GPS info were added later by me and is just a guess - also, I know this was in November 1991, not sure of day. I remember talking about the tide with an English nanny pushing a pram. Later spoke with a Polish man who wanted to talk about his friend Ernst Zündel, a neo-Nazi holocaust denier.