Battlefield 4 has a lot of Easter eggs in it. There's a goat from Jurassic Park outside the boundaries of one of the maps and someone is claiming to have found a T-Rex roar in the sound files, so who knows if there's a monster from all those years ago on land. Yet we do know for sure there's one in the ocean, as we have video and pictures of it. It's a Megaladon shark and it looks awesomely huge.
People believe it was added as part of the Naval Strike DLC package, so may have been added after people began looking for it, but it's not entirely clear.
If you want to find the Megaladon yourself, you need to do the following:
Head to the Nansha Strike map and during the storm phase, get 10 people around the boy at the very north end of the map... and wait to be crushed under the massive tonnage of a prehistoric predator.
This has been part of a big search that's been ongoing for a few weeks now, so a lot of effort went into finding this thing. What do you think of the results? Are they worth it?
You may think the image up the top along is enough, but then again, a LOT of work went into this. A lot.