Halimeda is indeed a Greek name, in Greek mythology she was a Nereid, daughter of Nereus and Doris. (Spelling in Ionian dialect: HALIMEDE, in Dorian dialect: HALIMEDA). The name derives from the words ALS(sea) and MEDEON (care of, protect, etc.), it means "cares for the sea". I can only tell you the ancient Greek pronunciation of the name: ha-lee-ME-da in Doric dialect or ha-lee-ME-dee in Ionian dialect. Unfortunately it is difficult to give you the precise "official" pronunciation using English phonology because English phonology is, how can I put it... very "flexible"!
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