Appeared to notice sea (6)
I believe the answer is:
seemed
'appeared' is the definition.
('seem' can be a synonym of 'appear')
'notice sea' is the wordplay.
'notice' becomes 'see' (I've seen this before).
'sea' becomes 'med' (abbreviation of Mediterranean**).
'see'+'med'='SEEMED'
'to' acts as a link.
(Other definitions for seemed that I've seen before include "'Appeared, gave the impression (6)'" , "Was appearing" , "Appeared, looked" .)