While in the Galápagos, inspect lava rocks and cliff ledges near the shoreline. You are certain to find brightly colored salt water crabs scurrying in every direction. The scientific name of the species is grapsus grapsus. Its common name is a lot more fun: Sally Lightfoot crab. Apparently, the crab’s amazing ability to run and leap in any direction to avoid predators reminded someone of the nimbleness of a Caribbean dancer. The width of the adult’s colorful shell (carapace) is three to five inches.