On April 14, 1912, ​in a perfect storm of engineering flaws, hubris and simple bad luck, the RMS Titanic descended into the depths of the North Atlantic Ocean roughly 400 miles south of Newfoundland, Canada. But while the Titanic has gone down in history, it wasn’t the only ship of its line to meet a watery end. In fact, 100 years ago today, its sister ship the HMHS Britannic also met its doom at sea.

As the sinking of the “unsinkable ship” made headlines, its owners at the White Circle Line already had its next Olympic-class counterpart in production. Originally called the Gigantic, its owners renamed the passenger liner with the slightly more humble name Britannic shortly after its predecessor sunk, according to History.com.

In the wake of the inquiries into how its predecessor failed so spectacularly, the Britannic underwent some big changes, including a thicker hull to protect against icebergs and the addition of enough lifeboats to accommodate everyone on board, according to History.com. However, it didn’t get much of a chance to redeem its sister ship as a passenger liner—shortly after the Britannic launched in 1914, the British government requisitioned it for use as a hospital ship in the early days of World War I.

As the largest of the British fleet, the Britannic wasn’t a bad place for soldiers to rest up and heal before heading back to the front lines. The ship’s ranking surgeon, a Dr. J.C.H. Beaumont, called it "the most wonderful hospital ship that ever sailed the seas," and with the capacity to carry and treat as many as 3,309 patients at once, British military officials figured the former passenger ship would be a great aid to the war effort, according to PBS.

On November 21, 1916, the Britannic was heading through the Aegean Sea to pick up wounded soldiers. But at 8:12 am, its venture came to an end with a blast. The source of the explosion is still unknown, but many believe the ship struck a mine left by a German U-boat.

The blast caused more extensive damage to the ship than even the Titanic had experienced, PBS reports. Only this time, thanks to the improvements made in the wake of that tragedy and the preparedness of the crew, many more lives were saved.

“The explosion occurred when we were at breakfast. We heard something, but had no idea the ship had been hit or was going down,” the Britannic’s matron, E.A. Dowse, told The New York Times a few days after the disaster. "Without alarm we went on deck and awaited the launching of the boats. The whole staff behaved most splendidly, waiting calmly lined up on deck...The Germans, however, could not have chosen a better time for giving us an opportunity to save those aboard, for we had all risen. We were near land, and the sea was perfectly smooth.”

The evacuation, however, was not perfectly smooth, according to History.com. The ship's captain directed the boat towards the nearest land with the goal of running her aground. But as the ship charged ahead, the crew attempted to launch several lifeboats unbidden. The ship's spinning propellers quickly sucked them in, killing those aboard the rafts. Even so, over 1,000 passengers escaped with their lives and the 30 people who died in the sinking of the Britannic stands in stark contrast to the more than 1,500 lives lost aboard the Titanic.

The disasters that befell the Britannic, the Titanic, and the pair's older sister, the Olympic, all had something (or someone) in common, Emily Upton writes for Today I Found Out—a woman named Violet Jessop. As a crew member and nurse, Jessop worked on all three ships, and miraculously escaped each one alive even though the incidents left two of the vessels nestled on the ocean floor. Having cheated death three times, Jessop eventually passed away in 1971 at the age of 84.