sea legs

noun[plural only]4

1. •
   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. •
   The ability to travel by ship without becoming seasick.
3. •
   The ability to partially or fully inhabit a marine environment.
4. •
   (US, rare) Synonym of crab sticks.