Bugs! One I know a little bit about and have published a littleresearch on. This is Ibacus alticrenatus, a slipper lobster. There’s a developing fishery for two species in this genus in Australia, and probably other regions, too.
Photo by Saspotato on Flickr. Used under a Creative Commons license.
Additional: Hm. Looking at this again, I wonder if this might actually be Ibacus peronii. This angle makes for a dramatic photo, but also makes it hard to tell the species.