Earlier this week, a while on a trip to the wreckage of the Titanic. The sub was , meaning rescuers are racing against the clock to locate the missing sub and from watery, claustrophobic hell. The latest update? They’re still down there.

However, rescuers have noticed a sound coming from beneath the North Atlantic, a set of “banging” noises . They’re hoping that this sound is related to the Titan sub, and that by finding the source of the noise they’ll also happen upon the sunken $250,000-per-seat tube. But, , seeking out the sound is tricker than it might seem:

Capt. Jamie Frederick of the United States Coast Guard said remotely operated vehicles are seeking the source of the sounds, and a team of experts is examining the noises to determine if they might be from the missing vessel. But so far, he said, that analysis has been “inconclusive.”

More rescue vessels have arrived in the vast search area — roughly twice the size of Connecticut and more than two miles deep — where teams of international experts have been conducting an extensive search for the craft, called the Titan. The 22-foot submersible lost contact on Sunday during what should have been a two-and-a half-hour journey to the wreck of the Titanic.

The New York Times also claims oxygen is truly becoming a concern. In the same updating piece, the Times quotes a United States Coast Guard admirable who estimates the occupants of the submersible may have a mere 20 hours of air left — less than a day to find the sub, pull it from the depths, and get its passengers some breathable air.