Complex sentence: Five sailing vessels were chartered and sailed out of Bremen with the members of the group, The Copernicus, The Johann Georg, The Republik, The Olbers, and The Amalia, the last and smallest, which foundered at sea and was never heard of again.
Split into simpler sentences: Five sailing vessels were chartered and sailed out of Bremen with the members of the group. These ships were named Copernicus, Johann Georg, Republik, Olbers, and Amalia, the last and smallest, which foundered at sea and was never heard of again.