I've always had trouble getting close to these guys, so I got excited when I found three of them in a tidal pool with pre-dawn light. They initially swam to the other side of the pond as I approached, but came back to my side after a few minutes.
Handheld resting against the sand using a borrowed 1.4x teleconverter
50D, 500 f/4 @700mm
1/200 sec, f/5.6, ISO 800