A massive search continues in the remote North Atlantic Wednesday for the missing Titan submersible with five people on board as the clock ticks for any remaining chance of survival.

The 21-foot unregulated submersible operated by U.S.-based OceanGate Expeditions has been missing since Sunday after losing contact with its topside support vessel approximately an hour and 45 minutes into its dive to the infamous Titanic shipwreck, located approximately 900 nautical miles East of Cape Cod.

According to the U.S. Coast Guard, the submersible was launched at 8 a.m. that morning and was expected to resurface at 3 p.m., but the vessel never resurfaced. The expedition support vessel Polar Prince reported the overdue submersible Sunday evening at 5:40 p.m. EDT.

Titan comes with an advertised 96 hours of life support. While the U.S. Coast Guard has stressed is only a single datapoint of many that are taken into consideration in the operation, based on that timeline the Titan has until Thursday morning before it runs out of oxygen—assuming a catastrophic incident hasn’t already occurred.

A Unified Command consisting of the U.S. Coast Guard, U.S. Navy, Canadian Coast Guard and OceanGate Expeditions is now coordinating the massive effort to find the missing submersible and return those on board home safely despite the odds.

During a Coast Guard media briefing Wednesday afternoon, USCG Capt. Jamie Frederick emphasized that the operation remains a search and rescue operation and said on-scene assets would be doubled within the next 24-48 hours, from five vessels to ten.

With that said, here are some of the vessels that are on scene or known to be participating in the search as of now:

TechnipFMC’s, Deep Energy, was the first commercial vessel to arrive on scene around 7 a.m. EDT Tuesday morning and began with remotely operated vehicle operations. The Deep Energy was delivered in 2013 as one of the largest and most capable pipe-laying vessels ever built.

ROV operations were being focussed near where underwater sounds were detected in the search area. The Coast Guard reported late Wednesday that an ROV from the UK company Magellan was set to join the search “in the near future.”

Horizon Maritime operates the Polar Prince, a former Canadian Coast Guard icebreaker turned expedition support vessel for OceanGate’s expeditions to the Titanic. The vessel is the one that reported the submersible missing and its has remained on scene throughout the search and rescue operation.

Horizon Maritime’s CEO Sean Leet gave a press conference on Wednesday providing additional insight into search operations so far. “The equipment that’s been mobilized for this is the finest in the world, the most capable in the world, and we have to hold out hope,” he said.

Horizon Maritime is also sending the Horizon Arctic, one of its highly capable offshore support vessels. Leet thanked charterer ExxonMobil for the support in providing the vessel to search and rescue. He said vessel loaded deepwater equipment, including an U.S. military ROV that was flown into St. Johns late Tuesday night. The Coast Guard confirmed the equipment includes the U.S. Navy’s Flyaway Deep Ocean Salvage System (FADOSS), a portable and motion-compensated lift system designed for deep ocean lifting for the recovery of large, bulky, and heavy objects such as aircraft or small vessels.

The Horizon Arctic departed the Port of St. John’s Wednesday morning at 5 a.m. “We are very aware of the time-density of this mission,” Leet said.

Arriving on scene Wednesday morning was the Canadian Coast Guard vessel CCGS John Cabot, a fishery science equipped with side scanning sonar, and the commercial vessel Atlantic Merlin, an anchor-handling tug (AHTS) owned and operated by Atlantic Towing.

The Canadian Coast Guard said it was also sending the heavy icebreaker CCGS Terry Fox and CCGS Ann Harvey, a buoy tending and SAR vessel equipped with a helicopter and pad, along with additional search and rescue equipment.

The commercial vessel Skandi Vinland has been on scene at approximately 7 p.m. local time Tuesday and got to work conducting search patterns, and is now working alongside the John Cabot and Atlantic Merlin. Skandi Vinland is a multi-purpose offshore support vessel that is operated by DOF and is equipped with two ROVs and an ROV operations team capable of providing 24-hour assistance.

Weather on scene today was reported as winds of 23mph with gusts up to 30 mph. Sea state is 6-7ft swells with an air temp of 50°f.

Other assets that are participating in the response, but not necessarily on scene, include the French research vessel L’Atalante, an ocean research vessel equipped with an ROV…

…and the Canadian Navy ship Glace Bay, a Maritime Coastal Defence Vessel (MCDV) equipped with a mobile decompression chamber and medical personnel.