The historic harbour in Carolinensiel is home to numerous vintage sailing ships and replicas. Most of these ships are privately owned and operated by their owners. Two of these vessels belong to the Sielhafenmuseum, the fishing cutter Gebrüder and the flat bottomed 'tjalk' Immanuel . Both boats were restored with the help of the Wittmund/Friesland education centre. They are operated and maintained by Mariner Guild Carolinensiel.

The fishing cutter Gebrüder AZ:5 was built in 1929 in Oldersum for ca. 13,000 gold marks. The 15 metre (50 foot) sailing boat with auxiliary engine is the last fishing vessel of its kind on the East Frisian coast. Its first owner, Georg Peters named the cutter in honour of his five sons, Gebrüder meaning 'male siblings'. AZ:5 is the old ID number used to identify high seas fishing vessels. 'A' stood for the municipality of Aurich and 'Z' for the home port of Neuharlingersiel.
Carolinensiel has been the home port of the Gebrüder since she was taken out of service in 1993. The historic vessel was restored and can today be booked for day trips into the Wadden Sea. The old wheelhouse of the Gebrüder is today part of the permanent museum exhibit.

The steel flat bottomed 'tjalk' Immanuel was built in 1912 in Dokkum, The Netherlands. Home ports for this small coastal freighter were Groningen and Leeuwarden. She was used primarily for transporting potatoes and vegetables in Dollart Bay, the River Ems and the Wadden Sea.

The Friends Society of the Siel Harbour Museum purchased the ship in 1991. It was restored and is fully operational today. With a draft of ca. 1 m (3 feet), tjalks are particularly suited for cruises in the Wadden Sea.