My dad was in the South Pacific during WWII. He said that his biggest fear was diving into his foxhole and finding a Coconut Crab in it. He said they could chop pieces off of a shovel with that claw.
I know an ex-Navy dude who stationed on Diego Garcia. He says those coconut crabs will stand in front of you with their claws open and dare you to pass. You have to run a half circle around them to avoid potential serious injury.