The US Coast Guard announced on Thursday that there were no survivors from the missing Titanic submersible, Titan, that vanished on Sunday while on a tour of the historic shipwreck site. All five people on board, including a British billionaire, a French explorer, and a father and son from Pakistan, are believed to be dead.

The Titan, operated by OceanGate Expeditions, was a 23,000-pound vessel and 22ft long that could dive to depths of 13,123 feet and carry five passengers. It was one of the few submersibles in the world that could reach the Titanic, which lies at about 12,500 feet underwater.

The submersible went off the radar about one hour and 45 minutes into its descent off the coast of Cape Cod, Massachusetts. The Coast Guard launched a massive search and rescue operation, involving multiple aircrafts and ships, but found no signs of life.

On Wednesday, a debris field was discovered within the search area, indicating that the Titan may have suffered a catastrophic implosion due to the immense pressure at the bottom of the ocean. Experts say that such an event would have killed the crew instantly.

The Coast Guard said that it was still investigating the cause of the accident and expressed its condolences to the families and friends of the victims. OceanGate Expeditions also released a statement saying that it was devastated by the loss and thanked the Coast Guard for its efforts.

The tragedy has sparked outrage and criticism from some quarters, who questioned the safety and ethics of such an expensive and risky venture. The Titanic submersible tour cost $250,000 per person and was seen by some as a symbol of extreme wealth and privilege.

Others defended the expedition as a legitimate and valuable scientific and historical endeavor, saying that it provided new insights and data on the Titanic and its preservation. The Titanic sank in 1912 after hitting an iceberg, killing more than 1,500 people.