Rescue efforts to find a submarine that was taking five passengers to the underwater Titanic wreckage site continued even as the 96-hour mark of oxygen supply inside the vessel ended. Rescuers have rushed more ships and vessels to the site of the disappearance, hoping underwater sounds they detected for a second straight day might help narrow their search. Lending to the efforts, France deployed a deep-sea robot while Britain embedded a submariner to find the missing vessel.

Deep sea explorer Dr David Gallo, speaking to a British news channel today morning, said that repetitive underwater noises were heard by three different aircraft with sensors for two-plus days. However, a US Coast Guard official said that while the sounds that have been detected offered a chance to narrow the search, their exact location and source haven’t yet been determined. Though the US Coast Guard said that authorities are still holding out hope of saving those onboard, estimates point to the oxygen in Titan running out as early as Thursday morning local time.

Lost aboard the vessel is pilot Stockton Rush, the CEO of the company leading the expedition, and his passengers are a British adventurer Hamish Harding, Pakistani father-son-duo Shahzada and Suleman Dawood, and a Titanic expert Paul-Henry Nargeolet. Newly uncovered allegations also suggest there had been significant warnings made about the vessel’s safety prior to its disappearance.

The Titan submersible went underwater at a time Newfoundland was witnessing its worst winter in 40 years, according to a Facebook post by British billionaire Hamish Harding ahead of the expedition.

“Due to the worst winter in Newfoundland in 40 years, this mission is likely to be the first and only manned mission to the Titanic in 2023. A weather window has just opened up and we are going to attempt a dive tomorrow. More expedition updates to follow IF the weather holds!” Harding wrote on Saturday.

If the Titan submersible is found, bigger challenges lie ahead, including retrieving its passengers and bringing the vessel to the surface.

Experts say that rescuing people through an underwater sub-to-sub operation is virutally impossible. Further, while robots deployed at the ocean floor can locate the sub, they cannot lift it to the surface. The robots can attach the sub to other vessels and ships that are powerful enough to lift it to the surface.

The Titan, the vessel that went missing in the area of the Titanic wreck in the North Atlantic on Monday (June 19), is classified as a submersible, not a submarine, because it does not function as an autonomous craft, instead relying on a support platform to deploy and return.

US Coast Guard’s Rear Admiral John Mauger told NBC’s Today show, “We continue to find in particularly complex cases that people’s will to live really needs to be accounted for as well. And so we’re continuing to search and proceed with rescue efforts.”

A NBC report quoted coast guard officials to add that new, high-tech vessels and medical personnel are moving to the search site.

The expedition costs $250,000 per person, which includes one submersible dive, private accommodations, training and expedition gear.

What is OceanGate, the company behind the missing submersible on a Titanic expedition? OceanGate Inc is a US-based company founded in 2009. Its website describes itself as “an ocean exploration venture focused on providing crewed submersible services to enable researchers and explorers to access the oceans’ vast resources”, adding that it plans to evolve methods to lower the costs of such explorations.

. The Indian Express