Marvel Studios has done a good job keeping whatever is happening with Iron Man 3 at the Port of Wilmington under wraps. The shoots have been taking place at night behind the barbed-wire topped fences at the Port of Wilmington. Security has also been patrolling the perimeter of the Port running away anyone who looks like they might be trying to catch a glimpse of the action inside. Rumors indicate that Marvel Studios is filming one of the biggest action sequences of Iron Man 3 at this multi-day shoot that started Friday night. We've also heard from a number of sources connected to the production that there is a major scene involving Iron Man swimming underwater, so this scene at the port could be the scene that leads up to Iron Man taking a dip in the ocean. Because of the night-time shoot and the fences, the most Comicbook.com has been able to observe is bright lights and lots and lots of smoke (check out our photos below). We've also heard the sound of gunfire and explosions. Local Wilmington news picked up a shot of a helicopter with some type of dome on the front flying overhead. Beyond that, the only clue as to what is going on comes from extras casting calls for the movie. The casting agency for Iron Man 3 has put out calls for fit athletic types and military types. In specific, they've requested an athletic male in his twenties to late thirties; a slender, athletic preferable blonde female; and an athletic, African-American female. One thing in common that they've requested from all extras is that they must be comfortable with heights. In some feel good news about the Iron Man 3 film, WHQR reports that Iron Man 3 has donated to the Wilmington Seamens Center. Apparently, Iron Man 3 used their building to plan movie shots and as rest stop for their crew. In exchange for using their facility, Iron Man 3 donated to the center's building fund, which will come in useful because the group is planning to move to a new location.