U-boat Type XXI, aka "Elektroboote", a submersible with 7 watertight compartments, increased battery capacity, tremendous underwater range. Much quieter than the Type VII. Had the Germans come up with this type submarine sooner, the outcome of the War might have been significantly different.
The U-2326 was a Type XXIII submarine of the German Kriegsmarine during World War II. 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.