- the main body of a sea or ocean, especially the part that is outside territorial waters and not enclosed, or partially enclosed, by land.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for open sea
At dawn we had completed most of the open-sea passage on the return journey.The Blocking of Zeebrugge
Alfred F. B. Carpenter
The open-sea or pelagic haunt includes all the brightly illumined surface waters beyond the shallow water of the shore area.
These open-sea young eels are known as Leptocephali, a name given to them before their real nature was proved.
Shipbuilding, including steamers for open-sea navigation, is on the increase.