The end of the Black Manta trailer shows the new character in front of a possible underwater point of interest. Since this chapter has focused on the Fortnite map being primarily underwater, having Atlantis as a new point of interest wouldn't be surprising.
Atlantis Landing Spot Possibly Leaked in Trailer
At the very end of the trailer, both Aquaman and the Black Manta are shown in front of something on the left side that is hard to make out through the water. It appears to be a potential new landing zone that fans speculate is Atlantis. Since the Black Manta is a villain, it is always possible that it is something more nefarious.
This leak could be related to the mysterious loot boat that has been moving around the map. Players should keep their eyes peeled for hints about where the new point of interest might be located and what might be happening towards the end of the season. The water level keeps changing, but something drastic will have to happen for an entire underwater city to surface.