The Nautilus story or How to tell the difference between a great hammerhead and a regular hammerhead.

While in PNG, we stayed at Tawali Resort.  The guides there trapped Nautilus shells for us one night and kept them in a bucket so that on the morning dive we could photograph or play with them and then let them float back to the deep.  Being such a small group, we each got our own shell.  I had decided to shoot mine with my 60mm lens and get some close-ups.  During the previous couple of days we had been seeing, from the surface only, this incredible solid white giant manta ray.  An elusive albino manta ray that I had been dying to photograph, but which never came by on our dives.  So in we get with our shells.  My dad was my dive buddy, but we had split up a bit so that he could video his shell, and I could photograph mine.   I hear him banging furiously on his tank and I know that he must have seen something incredible.  My first thought is of course that the albino manta ray is about to parade in front of my 60mm lens.  I looked up from the camera to see an enormous shark tail passing a couple feet from my head.  From the look of the tail, and growing up on a coast where bull sharks are prevalent, I  immediately thought - holy s*^#  that's the biggest bull shark that I've ever seen.  Then I signal this to my dad under water and he shakes his head and signals, no it's a hammerhead.  Just as I'm thinking, he must be wrong, this 12-14' hammerhead with a body as big around as horse, comes right by my camera again.  I guess it's only fitting that it came so close to me since I had been asking since we left the Maldives, where we saw several sizable hammerheads, how does one know the difference between a great hammerhead and a regular hammerhead?  I'm sure that there are many scientific distinctions between the two, but to put it in my terms the ones that make you stop and say holy S*^#! , are the great hammerheads, anything else is just a regular shark.  So you might be wondering why there's only a picture of a bucket of shells with this story.  You might as well know, I have no cool ability to get it together and take some radically new shot of a 12-14 foot animal with my 60mm lens, I just froze thinking, "is that thing real?!"  So that we never forget how amazing nature is and how much is in the ocean that we don't see,  I should tell you there were 10 of us on that dive with in very close proximity, but only 3 of us saw that magnificent shark!