Spotted maskray

The stingray has the ability to sense electricity and sweeps across the bottom searching for the electric pulses given off by the heartbeats of crabs.
Crabs, like us all, have a will to live and in an experiment they were hooked up to a lie detector test and when a shadow was passed over the top of them, their heartbeats slowed down.
Crabs can still their hearts so as to avoid being sensed by the stingrays.
Crabs would make great spies.
Upolu reef, Ocean Freedom