Look at the perspective. That thing is probably right next to the camera, and the boat is off in the distance a bit, giving it the appearance of a big shadow. Halfway up along the "body," a big portion is missing (Which, from what I'm reading is allegedly a wound, according to the original photographer in 1964, but where is the blood? Something that large should have a tremendous quantity of blood, which would be plainly visible in water of that clarity). Plus, that creature looks too big to be in water that shallow (I'm assuming that the photographer was on the shore?).

Another issue I have is the "eye" which can be seen on the "head" of the creature...if that is a "real" creature, it looks like it would be a large (giant?) squid of some sort (which would help to explain the "wound" as well, a bent tentacle, sounds nasty :p ).