In the Caymans they had a barracuda that had staked out the water around an underwater wreck called the Oro Verde, many years ago. They had given him a name, since forgotten. He circled me and scared the ba-##^%^ out of me. I had a hand on my dive knife, but, realized much later how futile that would have been.
Years later a friend of mine showed me something on a dive. A barracuda swam by and he pulled his dive knife out and let it drop to the bottom. The falling dive knife looks like a fish and the 'cuda turned to strike it and stopped inches away. I cannot tell you how FAST that animal moved. We really are in THEIR environment when scuba diving. SH