A small red squat lobster that swarms in open water in huge numbers, drifting rather than living on the bottom.
To about 8 cm, occasionally cited to 13. It is a squat lobster rather than a true crab: bright red and lobster-like but with the abdomen tucked under, and more closely related to hermit crabs than to lobsters.
Nothing else is encountered in swarms at the surface, so context identifies it.
What a diver meets is the swarm — open-water aggregations filtering plankton on the setae of their legs, occasionally forming red carpets a metre thick and tens of kilometres long in El Niño years, worked over by tuna, blue whales, sea lions and loggerhead turtles.
One flag. That swarming is a California Current and Baja phenomenon, and a Galapagos occurrence was not confirmed in the sources consulted.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
