(photo from here)
Cue the line for cocktail sauce! These little crabs are actually squat lobsters (similar to my favorite squat lobster, the yeti crab), and are also called 'langostilla'. They get the name 'tuna crab' because they're a favorite meal for tuna! (Mmmm, crab-stuffed tuna...) Anyways, warm ocean currents may have carried them too close to shore for these little guys to avoid getting beached, but this happens sometimes when they swarm together in order to mate. So... that didn't go so well for them...
(photo: John Gibbins)