This is the red hermit crab (Coenobita perlata) found on the beaches of the Cocos Keeling Islands.
They are relentless little scavengers that comb the beaches and vegetation behind, and easy to see when you sit on the beach watching sunset - they just appear around you. When camping on Pulu Keeling National Park they smell your cooking and come in large numbers to clean up on whatever they can get. Unwashed saucepans and plates are a favorite.
They get to reasonable size for a hermit crab, almost up to tennis ball size crab and shell together, though most are bigger than a golf ball.
Rob, Pulu Keeling National Park