at sea
confused:
I'm all/completely at sea with the new coins.

[TahlilGaran] Advanced Learner's Dictionary ▲

at sea
confused.
With no data they could depend on, they were utterly at sea.

[TahlilGaran] English Idioms Dictionary ▲

at sea
1. • at sea
to be on the sea, to be away on a voyage on the ocean
When my grandfather was a young man he was at sea for several months.

2. • at sea (about something)
to be confused, to be lost
Most of the class was at sea when the difficult theory was explained.

[TahlilGaran] English Idioms Dictionary ▲

at sea
adv. or adj. phr.
1. On an ocean voyage; on a journey by ship.
They had first met at sea.
2. Out on the ocean; away from land.
By the second day the ship was well out at sea.
Charles had visited a ship in dock, but he had never been on a ship at sea.
at sea² adj. phr. Not knowing what to do; bewildered; confused; lost.
The job was new to him, and for a few days he was at sea.
When his friends talked about chemistry, Don was at sea, because he did not study chemistry.
Compare: AT A LOSS.

[TahlilGaran] English Idioms Dictionary ▲