Proposed, too, to swim in the sea (6)
I believe the answer is:
mooted
'proposed' is the definition.
(I've seen this before)
'too to swim in the sea' is the wordplay.
'to swim' indicates an anagram.
'in the' indicates putting letters inside.
'sea' becomes 'med' (abbreviation of Mediterranean**).
'too' anagrammed gives 'oot'.
'oot' going inside 'med' is 'MOOTED'.
(Other definitions for mooted that I've seen before include "'Debated, considered (6)'" , "Raised question for discussion" , "Raised matter for discussion" , "Proposed for discussion" .)