Definition of "at sea"

at sea

prepositional phrase
1. Used other than figuratively or idiomatically: see at,‎ sea.
  Quotations
  It is never possible to settle down to the ordinary routine of life at sea until the screw begins to revolve. There is an hour or two, after the passengers have embarked, which is disquieting and fussy.
  1915, G[eorge] A. Birmingham [pseudonym; James Owen Hannay], chapter I, in Gossamer, New York, N.Y.: George H. Doran Company
2. (idiomatic) In a state of confusion or bewilderment.
  Quotations
  Wojciech Szczesny was then called into action twice in a minute to parry fierce drives from Djebbour and Torossidis as Arsenal's back four looked all at sea.
  2011 September 28, Tom Rostance, “Arsenal 2-1 Olympiakos”, in BBC Sport