Three widely separated groupings of these creatures were seen across the flats during low tide. They had the appearance of centipedes, presumably some aquatic form. They were all in very shallow pools of water and typically within close proximity to each other but with no interaction. The largest group had 6 individuals, none of which took any notice of us being close by. The head end is seen in the final two images and the approximate size can be gauged from the third image. Thanks to Barbara for the initial sighting.