Just like sand

 

I've encountered these amphipods a few times now and they're just magical!  It's amazing how much they look like sand.  

Not only because of the individual color patterns, with flecks to match the local sand grains, but also because they form dense aggregations and when nestled together they look just like a patch of sand.  

This is especially true when they're resting on a rock or a piece of seaweed — it's like "group camouflage"!  The background substrate disappears and you think you're seeing sand instead. Pretty impressive.

Here's an example (this time with a bryozoan in the background):

 

I'll be working on their identification, but for now it's fun to appreciate their remarkable color patterns.  If you have any ideas about which species this is, I'm very curious.