Elite Fire Barrels Help

#1AtomSmasher99Posted 11/3/2013 8:55:25 PM
I can't seem to find the elite fire barrel upgrade plan at the designated location(San Juan, it's a diving/smuggler spot at 479,487).
I've searched the entire place several times and I cannot seem to locate an area that resembles the picture shown on the treasure map(appears to be a cliff edge with a cave entrance adjacent to it). The only cliff edge I can find is the actual exit back to your ship, which you must dive into the water below from, as it goes nowhere else it seems.

To anyone who has the upgrade, could you help me out here?