At Sea Meaning

(idiomatic) In a state of confusion or bewilderment.

Example: At the ocean or sea, typically of a ship or person aboard a ship.
1915, George A. Birmingham, Gossamer, chapterI:
  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.
  Most of the class was at sea after the first week.‎
2011 September 28, Tom Rostance, “Arsenal 2-1 Olympiakos”, BBC Sport:
  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.