That crab was just following its instincts, but man, imagine if an octopus got involved. Those things are too smart, they'd probably try to unscrew a valve or something. Makes you wonder what other marine life sees our gear as prime real estate. Could have a whole squatting situation with a moray eel in a tool bucket. Nature just wants to use whatever we leave down there.
Had a buddy find a moray eel living in his tool bucket once. It just stared at him like he was the one trespassing. @taylor.reese is right about the squatting thing. Nature just takes over any space we leave behind. I bet if we left a wrench down there long enough, something would try to use it.