It's near the northern edge and has 2 chests and 2 data fragments. I can't seem to find my into the fort. There seems to be an underwater passage near it (without a diving marker), but I haven't unlocked the diving bell yet. --- http://ilikeorange.deviantart.com
Capturing that fort is a story mission. you can't do anything with it until then. --- sakamoto must be sacked. seriously "Real Fans" don't exist. Just another useless term fanboys throw around to get their "point" across.