I spotted this millipede-like creature in Hervey Bay, Australia at low tide, just kind of hanging out at the bottom of a small saltwater tidepool.
It's several inches long, composed of a large number of segments, each of which appears to sport a pair of legs.
Hard to tell from the photos, but the creature is aquatic and in both instances was observed moving around under about an inch or so of water. No specimens, alive or dead, were observed outside of the water.
They leave obvious trails behind them in the sand at the bottom of the tidepool as they move across it, and I assume they have some ability to burrow into the sand as I saw far more trails than I did creatures.
What are these things?