Astray on the ocean (2,3)

I believe the answer is:

at sea

I believe this clue is a double definition.

'astray' is the first definition.
(thesaurus)

'on the ocean' is the second definition.
(I've seen this before)

(Other definitions for at sea that I've seen before include "of no fixed abode" , "Bewildered; sailing" , "Confused, uncertain" , "Thrown" , "Travelling" .)

I've seen this clue in The Guardian.

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