The most important design legacy

What ship-design change was the best outcome of Titanic's sinking?

Double hulls and stronger compartmentation were the most important changes because they reduce the chance that one breach overwhelms a ship.

Double hulls and improved bulkhead design are identified as the most valuable changes. A double hull makes a single grounding or iceberg strike less likely to open the ship catastrophically. Better compartments contain flooding, strengthen the hull, and can create fire-resistant boundaries when designed properly. These changes place the deeper survivability lessons of Titanic alongside the more familiar lesson about lifeboats.