The Open Sea (OS) is the large open area connecting the many Ports and making travel between them possible.
It is single rendition of the Caribbean area. It includes the Atlantic Ocean from the Gulf of Mexico up to Bermuda in the North East and Guyana in the South East.
It has islands, Currents, ports and coastlines which are reasonably correct to their geography and historic location.
Traveling the Open Sea goes reasonably fast. The time it takes to travel the length of the map will depend on the Ship you are using, where the Wind is blowing from and where you are heading to, if you are using the currents and if you have Modifications to increase the OS speed. It takes more of less 2 hours in a Ship of the Line but maybe less than an hour in faster ships.
Just like ports the open sea is Persistent (as opposed to Instanced) and Players can see each other and even engage in activities together like forming Groups and engaging Non-Player Character (NPC) Fleets or other players.
The open sea is filled with traveling NPC fleets and the occasional Player.