See NBC News
The scientists need to find what Gallo calls the “center of the haystack” before they can begin a search for the needle. And even then, it remains to be seen whether the search will be in deep or shallow water. Each requires a different set of equipment, and the process is slow and requires painstakingly meticulous work. It took Gallo and his team two years to find the fuselage and flight recorder of Air France’s crashed jetliner.