Cerulean Ocean is one of three oceans released on January 31, 2012. The ocean is a subscription ocean created through the merger of the Midnight and Cobalt Oceans, and open testing lasted from January 4 to January 9, 2012.
The mergers of the English-language oceans were hinted at on December 7, 2011, when the "Intrepid Explorer" Velasco Thorsson posted his journals on the Hear Ye! Announcements forum. The mergers were subsequently announced the next day by Hermes. On the same day, voting on the new oceans' names opened to the general public, who voted on the name "Meridian" for the Viridian/Malachite merger, "Emerald" for the Sage/Hunter merger, and "Cerulean" for the new subscription ocean.
Cerulean has one hundred and thirteen islands divided among eleven archipelagos. There are sixty-seven colonized islands. The area that comprises the former Cobalt Ocean has the same geography as the former Viridian Ocean and the late Crimson Ocean.