The German Type XXI U-boat had a deep diving depth of 280 meters (919 feet).

German is. Submarine is not.

"A German submarine surfaced in the North Sea."

Yes - though most had manual reload capability, the German Type XXI U-Boat, which never saw active service, was the first true submarine with hydraulic reload capability. It was also the first true submersible, featuring a streamlined hull, no deck guns, and designed for running submerged as normal operation rather than just for attack purposes. Many of her features were the forerunners for today's modern submarine systems and design. Her sail is reminiscent of Russian submarine sail design.

German submarine U-A was created in 1939.

Lusitania wasn't a German submarine, it was an American merchant ship that was sunk by German submarines.