The Titan 4000M is a Cyclops-class manned submersible designed to take five people to depths of 4,000 meters (13,123 feet) for site survey and inspection, research and data collection, film and media production, and deep sea testing of hardware and software.
Oceangate Expedition lost communication with the Titan on 18 June 2023 while diving to the Titanic wreck site . . . 5 people onboard.
Note: Titan only has one point of entry - the forward viewport, attached by 17 bolts - accessible only from outside the vessel.
At the time Aaron made this video the fate of the 5 people onboard the Titan was unknown.

