The co-founder and Board chair of Horizon Maritime, the company that owns the Polar Prince boat that took the Titan submersible out to sea, is speaking out.

"We have been supporting the Titanic expeditions for several years," Sean Leet said, calling the Polar Prince "an iconic former Canadian Coast Guard icebreaker that has been upgraded with advanced technology."

"All protocols were followed" for the submersible's mission, he said at a news conference Wednesday, calling the missing sub an "unprecedented" situation.

Equipment heading to search site can reach the depths of the submersible and potentially take it to the surface, he said.

"We wish to thank everyone involved in this rescue mission, especially the U.S. and Canadian Coast Guards, the organizations that have made their marina assets available including the French government … [and] the many private companies that have dropped everything at a moment's notice," Leet said.

"Our thoughts and focus remain with the crew of the Titan and their families," he said.

Leet said he is holding out hope that the five-person crew will be brought home safely.

"We'll continue to hold out hope until the very end," he said.

As crews scour the Atlantic Ocean for the missing submersible, the U.S. Coast Guard said it's searching in the area where underwater noise was detected.

The unidentified noise was detected Tuesday night and Wednesday morning.

The data on the noise was sent to the U.S. Navy to be examined, according to the Coast Guard.

"We have to remain optimistic and hopeful when we're in a search and rescue mission," Capt. Jamie Frederick, the First Coast Guard District response coordinator, said at a press conference on Wednesday afternoon.

The deep-sea vessel submerged on Sunday morning with five people aboard and a 96-hour oxygen supply, according to the Coast Guard. That amount of breathable air is forecast to run out on Thursday morning.

When asked about the search becoming a recovery mission, Frederick told reporters: "We're not there yet."

One of the ships the Canadian Coast Guard sent to the rescue effort, the John Cabot, is equipped with advanced, deep sonar, said Joyce Murray, minister of Fisheries, Oceans and the Canadian Coast Guard.

"We've sent so many assets to the search team to help," Murray said. "Authorities still have hope in the mission."

-ABC News' Will Gretsky

Mike Reiss, who has done four, 10-hour dives with OceanGate, including one to the Titanic, told ABC News his sub lost contact with the host ship on every dive.

"Every time they lost communication -- that seems to be just something baked into the system," he said.

With no GPS, Reiss said it took his crew three hours to find the Titanic despite landing just 500 yards from the ship.

Reiss said he signed "a waiver that mentions death three times on the first page.”

"It is always in the back of your head that this is dangerous, and any small problem will turn into a major catastrophe," he said.

He said the submersible is built simply and is "just propelled by two fans on the outside."

"Even I was able to steer and navigate the sub for a while," he noted.

Reiss said his greatest fear was that the sub wouldn’t be able to release the weights that force it to submerge once it was time to rise to the surface.

-ABC News' Gio Benitez and Sam Sweeney

OceanGate co-founder Guillermo Söhnlein is coming to the defense of late CEO Stockton Rush, one of those killed in the implosion of Titan, after criticism from director James Cameron, and others, who said the sub's carbon-fiber hull was dangerous.

"In this kind of community, there are completely different opinions and views about how to do things, how to design submersibles, how to engineer them, build them, how to operate in the dives," Söhnlein told the U.K.'s Times Radio on Friday. "But one thing that’s true of me and the other experts, is none of us were involved in the design, engineering, building, testing or even diving of the subs. So it’s impossible for anyone to really speculate from the outside."

Söhnlein co-founded OceanGate in 2009 with Rush and led several dives in the early days of the company. He left OceanGate in 2013, when Rush took over as CEO, but maintained a friendship and spoke to Rush just weeks before the doomed expedition, he said on Facebook.

Cameron, who not only directed the Oscar-winning film "Titanic" but is a prolific ocean explorer, criticized the use of a carbon-fiber hull in the construction of Titan, saying it was only a matter of time before it cracked under the pressure from repeated dives. Rush, in the past, defended its use, saying it had a better strength-to-buoyancy ratio than titanium.

"I was involved in the early phases of the overall development program during our predecessor subs to Titan, and I know from firsthand experience that we were extremely committed to safety and risk mitigation was a key part of the company culture," Söhnlein told Times Radio Friday.