Italian officials have given the go-ahead to an attempt to right the Costa Concordia, the cruise ship that capsized off the island of Giglio 20 months ago, early Monday morning. The operation—a maneuver known as "parbuckling"—is risky in that its never been tried on a ship this size and once initiated can't be stopped. It's one-and-done, regardless of the result.

The parbuckling technique involves welding steel boxes, known as "sponsons," to the high side of the ship and filling them with water. Then the ship will be pulled onto and underwater platform, have steel boxes welded to the other of the ship, and drained of its water. Once the ship reaches a 25-degree angle, engineers hope that gravity will do the rest. Nick Sloane, salvage master for the operation, said, "We are not sure about the actual weight and how much the rocks are going to hold onto her."

In addition, pollution from the ship is a concern:

Since the shipwreck, no major pollution has been found in the waters near the ship. But should the Concordia break apart during the rotation — a possibility authorities describe as remote — absorbent barriers have been set in place to catch any leaks. Fuel was siphoned out early in the salvage operation, but food and human waste are still trapped inside the partially submerged vessel and might leak out.

In addition to possible human waste, the bodies of two of the 32 fatalities due to the accident have not yet been recovered, so salvagers are on the lookout for those as well. CNN has a step-by-step interactive explanation of the entire operation.

It's already morning in Italy, and Reuters has a livestream of the salvage.