Noun
That part of the sea out of sight of land.
A sea open to all nations, i.e. not a mare clausum.
Source: en.wiktionary.orgA woman knows the face of the man she loves as a sailor knows the open sea. Honoré de Balzac
Writing criticism is to writing fiction and poetry as hugging the shore is to sailing in the open sea. John Updike
The house was built on the highest part of the narrow tongue of land between the harbor and the open sea. It had lasted through three hurricanes and it was built solid as a ship. Ernest Hemingway
I had a certain cetacean delicacy of movement in the wide open sea of a hundred-yard field... Michael Chabon
You do not ask a tame seagull why it needs to disappear from time to time toward the open sea. It goes, that's all. Bernard Moitessier
Puberty for a girl is like floating down a broadening river into an open sea. G. Stanley Hall