Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. German Type XXIII submarines were the first so-called elektroboats to become operational. They were small coastal submarines designed to operate in the shallow waters of the North Sea, Black Sea and Mediterranean Sea, where larger Type XXI Elektro boats were at risk in World War II. They were so small they could carry only two torpedoes, which had to be loaded externally.