We don't have synonyms for sea-legs yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are seamless, sea legs and seatless.
(n) :
Alternative form of sea legs. [(idiomatic, nautical) The ability, when walking aboard a ship, to anticipate the motion of the deck so as to walk steadily without losing balance.]
(n) :
Alternative form of sea legs. [(idiomatic, nautical) The ability, when walking aboard a ship, to anticipate the motion of the deck so as to walk steadily without losing balance.]