The Titanic tourist sub was built by a Seattle man's company based in Everett

The clock is ticking ominously as rescue crews surveil the North Atlantic for a possible sighting of the Titan, a unique submersible watercraft that was built by OceanGate Inc., an Everett, Washington, company.

The vessel's captain is Stockton Rush, CEO of OceanGate and a Seattle resident who records show lives in Madison Valley.

The Titan descended into frigid Atlantic waters on Sunday with five people aboard — it has been described as a van without seats with a bubble window at the end for viewing. Those aboard hoped to see wreckage of the Titanic, which sank in 1912.

Rush uses a repurposed videogame controller to drive the Titan down to the Titanic wreckage spot, which is submerged 2.4 miles below sea level.

The sub has a 96-hour oxygen supply (four days) for five people and is expected to run out of breathable air by Thursday morning.

The University of Washington's Applied Physics Laboratory worked with Rush and OceanGate from 2013 to 2020, a spokesperson said. They worked on an earlier version of the sub, a shallow diving submersible called CYCLOPS.