Complex sentence: His ship shored in New Guinea, one of the Pacific Islands known at that time, they received some food and water from the natives and they sailed again northeast where they discovered the Marshall Islands and Admiralty Islands.
Split into simpler sentences: His ship shored in New Guinea, one of the Pacific Islands known at that time. There they received some food and water from the natives and they sailed again northeast where they discovered the Marshall Islands and Admiralty Islands.