Let your imagination run free and you are walking along at the tides edge on a beach (here it is Aberystwyth) the tide rushes in and unless you are paddling and happy to let it run over your feet you retreat hastily to avoid your shoes getting wet. Trying of course not to make a fool of yourself like Neil Kinnock. Then the tide flows back through the pebbles making that unique rattling/sucking sound ~ this photograph captures that moment ~ ideally it needs the sound effect as well.
It's an image that for me brings back memories. Not only of that day on the beach at Aberystwyth but when I was a kid playing on the beach at Lowestoft. Perhaps it releases some memories for you.