The Old Man scenario drops you into Tanoa's 100 km² tropical jungle island terrain with only a few instructions. It's your own decisions and gut feeling that will decide your path. Obtain intel, gather weapons and equipment, and tackle your objectives at your own discretion. The beta version of this scenario is now available for download on the ARMA 3 Steam Workshop. As it is still beta, you can file game issues to the Arma 3 Feedback Tracker.
More info? Check out the official website.