sea-legs

Noun

sea legs pl (plural only)

1. (idiomatic, plural, plural-only) The ability, when walking aboard a ship, to anticipate the motion of the deck so as to walk steadily without losing balance.
   • to get/find one's sea legs
2. (idiomatic, plural, plural-only) The ability to travel by ship without becoming seasick.
   • When the ship was pitching or rolling, work would be difficult; but even then, when the Colonists get their sea-legs, and are free from the qualmishness which overtakes landsmen when first getting afloat, I cannot see why they should not engage in some form of industrial work far more profitable...1890, William Booth, In Darkest England and the Way Out
3. (US, plural, plural-only, rare) Synonym of crab sticks.

   Synonyms:

   crab sticks

4. (idiomatic, plural, plural-only) The ability to partially or fully inhabit a marine environment.
   • So, from the Jurassic Period to today, the problems that come with being secondarily aquatic seem to have had the same kinds of solutions. And what we've learned is that it's no easy task to get your sea legs. But once you do, it's smooth sailing.2021, PBS Eons: When Crocs Thrived in the Seas