>> 20 minutes into the dive, the playful emma becomes agitated, swimming more quickly and becoming more aggressive about getting fed. >> this is when the moray eel swam around the back of me. she could smell the food, saw my thumb and thought it was some sausage or food and she latched only my thumb. and i guess it took five or six seconds. a large popping sound, it came clean off. >> like all moray eels, emma has really bad eyesight. matt thinks she simply can't tell the difference between his thumb and lunch. but moray eels have another, more deadly weapon than just a fine set of choppers. emma bites down with her first set of jaws and then the second jaw buried deep in her throat severs his thumb. matt's thumb doesn't have a chance. >> once they bite, it's very difficult to -- well, in my case, it was impossible to get my thumb out of the moray's