Wildlife Spotting

Aquatic worm. 3-5 mm long. Two, possibly more protrusions at one end. Worm could completely turn itself around inside shell. Cylindrical "shell" of circular plates (photo close-up). Used Transparent tongue-like extension about 2 mm long to reach out, stick to slide and pull itself along. Saw multiple, much smaller protrusions extend occasionally from other end of "shell". Also had multiple small transparent blob-with-foot extensions clinging along plates. Fast moving, could propel itself several mm in seconds. Could not see body as it was inside "shell", which could have been constructed rather than grown as bits of sand were attached as well.