The crew has urged vessels in the wide expanse of the Atlantic to report any potential clues they might spot.
The vague rule of thumb is that humans can survive three days without water and three weeks without food, one expert said, but examples defying that abound — especially if people have supplies, wear life jackets or can cling to something.
By Wednesday, it still wasn't clear if 14-year-olds Perry Cohen and Austin Stephanos fell into any of those categories.