Noted rescue ship in sea ... (6)
I believe the answer is:
marked
'noted' is the definition.
('mark' can be a synonym of 'note')
'rescue ship in sea' is the wordplay.
'rescue ship' becomes 'ark' (Noah's ark).
'in' is an insertion indicator.
'sea' becomes 'med' (abbreviation of Mediterranean).
'ark' going inside 'med' is 'MARKED'.
(Other definitions for marked that I've seen before include "showing flag maybe" , "Read, corrected and awarded a grade" , "Singled out; clearly noticeable" , "Easily noticeable" , "Pronounced" .)