SKIDAWAY ISLAND — More than 15 miles from the inlet marshes of Savannah and shores of Sapelo Island, like a drop of gray on a vast blue canvas, the enormous Nancy Foster research vessel bobs steadily atop the surface of the Atlantic Ocean. Views in every direction reveal rolling, reflecting waves of water that stretch to the horizon and a scene quiet and devoid of any activity. But near the Nancy Foster, commotion is constant.