I dove back in the days when there were actually LOTS of sharks around and had them follow me on occasion with no incidents. Within the past few years I've even had a great white swim behind me (as attested to by my dive buddy Wyland on that dive). I still have all nine fingers. Non-hunting SCUBA divers are generally not at much risk except in certain regions of the world and with certain species (although any shark, including a nurse shark, may defend itself if provoked).
As for the great whites "attacking" from below, this may be true in many cases (mostly ones where boaters actually witness an "attack" on a marine mammal swimming at the surface. However, they also attack from behind at the same depth (as witnessed by a friend who saw a GWS take a sea lion midwater) and even from above (I've seen bite marks on the backs of giant sea bass which hover near the bottom and are eaten by GWS and probably large makos).
I like to film sharks myself, although there are some species I admit to being a bit leery around.
