On May 31, 1911, the British liner Titanic slipped into the water for the first time. Nearly a year later, on April 10, 1912, it sailed out of Southampton, England, at the start of its doomed voyage (pictured above). (AP)

Shipbuilder Harland & Wolff’s shipyard was a flurry of activity that day, with special grandstands constructed for important guests, a cursory inspection of the ship by H&W partner Lord Pirrie, and an inch of tallow and soap used to lubricate the slipway for the liner.

The RMS Titanic was still incomplete. The massive hull with engines and boilers had none of the finished luxurious rooms that would later become a hallmark of the ship. But after three years of round-the-clock work by 3,000 Irishmen, the liner was going into the water all the same.

“We just builds ‘em, and shove ‘em in,” a shipyward worker said that day.

As ‘Good Luck’ flags fluttered, and rockets were fired, the supporting timbers were knocked free. Workers leapt from under the hull as the enormous beauty slipped into River Lagan.

The “unsinkable” Titanic was in the water, and it was floating high.

A shipyard worker, James Dobbins, was injured by falling timbers during the launch, but few noticed as celebrations began in earnest at the city’s Grand Central Hotel. Dobbins died later that day, the first indication that something might not be just right with the liner.

In Belfast today, 100 years later, a religious service is being held at the Harland & Wolff shipyard to mark the anniversary.

No survivors of the sunk Titanic remain. The last living survivor — Millvina Dean, who was eight weeks old when the ship set sail — died at 97 in June 2009.