Alfred Scott McLaren is a retired U.S. Navy Captain who has spent nearly six years underwater in submarines. He's also a submersible pilot who has visited the wreck of the Titanic twice.
He spoke with Scripps News about the noises someone aboard a submarine might encounter.
"I remember from my submarine days we get lots of strange noises down there," McLaren said. "One of the things that used to drive us nuts is something called carpenter fish. It sounded like carpenters banging on wood or pipe or things like that. There are a lot of marine noises that could be confused. The fact that this was detected at half hour intervals is encouraging."
McLaren also discussed potential scenarios that the crew of the submersible might encounter. He said even if the submersible is on the surface, it could be difficult to locate.
"In all the operations I've done, whether it's submarines or submersibles, protocol is if you lose communication, you go to the surface," McLaren said. "Now that submersible, once it got to that surface … there probably is hardly anything projecting above the water. And you're there in that sea state and light fog. It could be up there on the surface all this time and you still haven't found it."
McLaren said other possibilities include that the submersible has become stuck in the wreckage of the Titanic, which is fragile and prone to deterioration. The submersible may also be stuck in the silt at the bottom of the ocean, which can trap vessels that don't have enough power to free themselves.
McLaren said open questions include whether the submersible has any drop weight, which could be released to increase its buoyancy and help it return to the surface.
As of Wednesday, officials have searched an area of the Atlantic Ocean more than two times the size of Connecticut. Officials said Wednesday the operation is still considered a search and rescue. Oxygen reserves aboard the submersible were expected to last until Thursday morning, if they're in good working order.
