Just curious if there was a trick to finding Great Whites, or if Ive been unlucky. Never even seen one before now, and Im not exactly new to the game. Seen plenty of the other sharks, but never the GW. Where are they?!? 
I have come across one at night and I was near the northernmost boundary.
Those are actually a hard find. I’ve seen one (and was terribly unprepared at the time) the next best thing in my opinion is the Tiger Shark which is much more common along with the Goblin Shark, Reef Shark, and Hammerhead Shark. So I would keep an eye out in odd places and deeper water.
They typically appear in the open ocean, not around wrecks or islands, and are very rare. I think you’ll really just have to be lucky to run into one.
I have only spotted one once in the I don’t know how many hours of gameplay.