Soldier Crabs

 

Soldier crabs aren't that common near civilzation these days.

Their swarms appear to be smaller, a couple of hundred

instead of thousands; and the individuals are a lot smaller.

This one is about 15mm instead of 25mm 

and he was one of the biggest of the bunch.

 

When they realise they can't outrun you they hide by burying 

themselves in the sand. They do this by scooping the sand out from 

underneath them and rolling it up into little balls while rotating clockwise.

A sand igloo quickly covers them, and because the sand's wet it blends together. 

Several seconds later you can't tell where they burrowed in.