Complex sentence: It was identified in Greek mythology with the "Argo", the ship used by Jason and the Argonauts that sailed to Colchis in search of the Golden Fleece.
Split into simpler sentences: It was identified with the "Argo", the ship used by Jason and the Argonauts in Greek mythology. The ancient Greeks identified it with the ship sailed by Jason and the Argonauts to Colchis in search of the Golden Fleece.