One hundred years ago, the Britannic, the sister ship to the Titanic, sunk in Aegean Sea. At the time it was being used by the British as a WWI hospital ship. While 30 people were killed, more than 1,000 were rescued after the ship suffered a violent explosion. The reason so many more lives were spared is because unlike the Titanic, the Britannic was mandated to have enough lifeboats onboard for all of its passengers. What caused the Britannic to sink remains a mystery to this day. Read the prevailing theory as to what sunk the ship.