So confused in ship (2,3)

I believe the answer is:

at sea

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'so confused' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for at sea that I've seen before include "sent in junk?" , "on board" , "stumped" , "Totally disorganised" , "Worse things can happen here" .)

I've seen this clue in The Sun.

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