Yes Blue Devil - fast moving sharks create a whole new range of problems for digital cameras. I must admit that, during the dive, I was thinking my old Nikononos with a wide angle lens would have yielded more (but not necessarily better) images. Trying to get a digital to focus on the fairly featureless side of a Silvertip less than arm's length away was the most frustrating bloody thing I've experienced in photography - I found it best to pre-focus on something stationary and then hold....wait...shoot. But it ain't easy. Regarding the camera "locking up" - that is a mechanism that automatically engages whenever you have the potential to take the world's best ever shark photos. Either that or it was probably user-error - the 'idiot filter'.