As US and Canadian authorities continue search efforts overnight, it is still not clear what happened to the missing submersible, why it lost contact with crews on the surface, and where — or how deep — it might be.
Eric Fusil, a submarine expert and associate professor at the University of Adelaide, said the search is complicated by limited underwater communication methods with the submersible.
"As there is no tether between the Titan and the support surface ship, the only way to communicate or detect from the surface is through the sea water," he said.
Above the water, in open air, detecting objects like the submersible can be "instantaneous" thanks to radar and other communications across long distances, he said — but underwater, "spotlight or laser beams are absorbed within a few meters."
That means no radar or GPS is available, either, he said.
A submersible like the Titan would therefore have to rely on acoustic sound sensors and basic communication like text messages, he added.
When communications break down: When CBS correspondent David Pogue took a trip on the Titan to the Titanic wreck last year, he said the submersible was only guided by text messages from the surface ship. On Pogue’s trip, communications broke down during a dive and the submersible was lost for more than two hours, he said.