The Megalodon has returned to Battlefield 4, now making its massive shark home on the Paracel Storm map. The easter egg has been discovered by those in the community test environment, and it was added to celebrate the 100th patch coming to the CTE:
The Megalodon previously appeared in the Naval Strike expansion for BF4, scaring the bejeesus out of anyone who hit some strict criteria on the Nansha Strike map. It was removed from the game quite a while ago, and I did think it was relatively safe to go for a paddle once more.
Apparently not. There's no word if the Megalodon will make its way into the game proper and stay there, but seeing as EA is happy to patch out all the fun we have in Battlefield, I wouldn't hold my breath.