The Collaborative International Dictionary
Sea room
Sea room \Sea" room`\ (Naut.)
Room or space at sea for a vessel to maneuver, drive, or
scud, without peril of running ashore or aground.
--Totten.
Wiktionary
sea room
n. The space at sea necessary to manoeuvre a ship.
WordNet
sea room
n. space for maneuver at sea
Usage examples of "sea room".
Hard to beat off, unless she fired up Max the engine and won free that way, got some sea room for tacking.
The further out we hit them, the more sea room I'm going to have to handle this brute in.