Feeding predatory fish underwater can be extremely dangerous. An Australian diving instructor experienced this at first hand. When feeding a moray, the animal grabbed his thumb and didn't want to let go. At that time it was still a matter of seconds. Watch how the bizarre second jaw mechanism of a moray eel works. Watch the film:
Second jaw mechanism moray eel
A moray doesn't just swallow its prey. While the animal holds the prey with its mouth, a second jaw mechanism (with teeth and all) shoots forward from its throat to pull the prey in at once. The unfortunate diving instructor experienced this as a sudden pull, after which his thumb broke off and the moray swam away with it. Morays are almost blind and rely mainly on their sense of smell. Attempts to loosen his thumb failed, the teeth of a moray eel are razor sharp and face inwards.