On March 28, 2015, researchers onboard the NOAA Ship Nancy Foster launched an autonomous underwater glider—commonly called an ocean glider—into the waters off St. Croix. The glider will spend 20 days at sea on a solo mission to collect environmental data. During this mission, the main goal of the glider is to locate places where economically and ecologically important fish such as snappers and groupers are gathering to spawn in time with the lunar cycle. During spawning, some species of fish make grunting sounds. The glider uses an ambient acoustic sensor to "listen" for these vocalizations. Since the NOAA ship can't be everywhere at once, the glider serves as an extra set of "ears" that allows researchers to search for aggregations of fish over a much larger swath of ocean.