Complex sentence: Those who heard her description of the Captain couldn't believe such a person could exist in New Zealand; before being appointed in command of HMNZS Waikato in 1977, and as Captain, Eleventh Frigate Squadron.
Split into simpler sentences: Those who heard her description of the Captain couldn't believe such a person could exist in New Zealand. He was appointed to command of HMNZS Waikato in 1977, and as Captain, Eleventh Frigate Squadron.