At low tide, hundreds (if not thousands) of Blue Soldier Crabs leave their burrows and march across the beach... they are one of the only crabs that can walk straight forward, instead of sideways. ... They are known as soldier crabs because they all "march" together across the sandy mud flat. Their large numbers are thought to help protect them from predators.
Thanks to all Phoide contributors to Brisbane Water!
Most notably David Hamments.