Wiktionary
n. (context informal English) The sense of balance, slowly regained after a time at sea.
Wikipedia
Land Legs is a 2015 French drama film written and directed by Samuel Collardey. It was screened at the 72nd Venice International Film Festival, where Dominique Leborne was awarded best actor in the Horizons section.
Usage examples of "land legs".
At this point the continents split and rapidly separated east and west, leaving a green ocean between their land legs, dotted with several large islands and driblets of isles in the southern hemisphere.
WHILE THE LATEST ARRIVALS were getting their land legs and accustoming their stomachs to the good British grass, there was much to do in preparation for the journey.
Meanwhile, the crew staggered like drunks, trying to regain their land legs after centuries of perpetual storm at sea.
I had also reacquired land legs and the ground under me no longer had even the slightest rocking motion.