From Longman Dictionary of Contemporary English(all) at sea(all) at seaCONFUSEDconfused or not sure what to do Living in a foreign country can mean you’re always at sea about what’s going on. → sea
Examples from the Corpus
(all) at sea• This week, however, when you find yourself all at sea, you may wonder whether you've chosen well.• We are glad to be with them again, especially when they are at sea.• A girl from near his village in Trondheim fell ill the first day at sea.• His eyes were an astounding blue and his complexion was ruddy from a life spent mostly at sea.• Down to the beach to see the oil rigs at sea.• Teredo, or shipworm, can have a devastating effect on the hulls of wooden ships at sea.• At worst, they can sink or lose their nuclear warheads at sea. 