(NewsNation) — A search is underway for a deep-sea vessel that went missing Sunday with five people aboard after it dived toward the wreck site of the Titanic ocean liner.

The Coast Guard said there were one pilot and four “mission specialists” aboard. “Mission specialists” are people who pay to come along on OceanGate’s expeditions. They take turns operating sonar equipment and performing other tasks in the five-person submersible.

Among the passengers of the submersible, called the Titan, is Hamish Harding, a 58-year-old British businessman. Harding lives in Dubai in the United Arab Emirates, according to Action Aviation, a company for which Harding serves as chairman.

Harding is an adventurer who holds three Guinness World Records, including the longest duration at full ocean depth by a crewed vessel. In March 2021, he and ocean explorer Victor Vescovo dived to the lowest depth of the Mariana Trench. In June 2022, he went into space on Blue Origin’s New Shepard rocket.

NewsNation confirmed the CEO and founder of OceanGate Expeditions, Stockton Rush, is among the passengers, along with Pakistani businessman Shahzada Dawood and his son Suleman. The fifth person is believed to be Paul-Henry Nargelot, the submersible’s pilot.

An initial group of tourists in 2021 paid $100,000 to $150,000 apiece to go on the trip. OceanGate’s website described the “mission support fee” for the 2023 expedition as $250,000 a person.

Titan is capable of diving 2.4 miles “with a comfortable safety margin,” according to documents filed by the company in April with a U.S. District Court in Virginia that oversees Titanic matters.

The sub has an oxygen supply that should last for four days and a real-time monitoring system that analyzes the pressure on the hull and integrity of the vessel.

In a May 2021 court filing, OceanGate said the Titan had an “unparalleled safety feature” that assesses the integrity of the hull throughout every dive. At the time of the filing, Titan had undergone more than 50 test dives, including to the equivalent depth of the Titanic, in deep waters off the Bahamas and in a pressure chamber, the company said.

During its 2022 expedition, OceanGate reported that the submersible had a battery issue on its first dive and had to be manually attached to its lifting platform, according to a November court filing.

The goal of OceanGate’s expeditions has been chronicling the Titanic’s deterioration as well as the underwater ecosystem that shipwrecks often spawn.

What’s left of the Titanic is slowly succumbing to metal-eating bacteria that consumes hundreds of pounds of iron a day. Holes pervade the wreckage, while the crow’s nest is already gone. Some have predicted the ship could vanish in a matter of decades as holes yawn in the hull and sections disintegrate.

The company outfitted the Titan with high-definition cameras and multi-beam sonar equipment. Charting the wreck’s decomposition can help scientists predict the fate of other deep-sea wrecks, including those that sank during the world wars. Another focus is the sea life: Hundreds of species have only been seen at the wreck.

The Associated Press contributed to this report.