Lettre D. Metaphor would be correct.
A metaphor occurs when someone substitute a word's usual meaning by another, applied only through implied comparison, with the intention of giving a somewhat poetic tone to the message.
Although it's not clear by the excerpt provided what meaning the author actually meant to imply for 'babes of the sea', it is clear that 'babes' in this expression do not carry its orginal meaning ('child'; 'girl').
