Transfer of External Torpedoes at night

This has been discussed before and I thought it not possible. But, I came across the first written documentation that external torpedoes might have been transferred at night.

The history and career of U-175, Type IX, is covered in the book: Shadows on the Horizon: The Battle of Convoy HX-233 (ISBN: 1840675241) by W A Haskell. U-175 was sunk during an attack on HX-233 and therefore was written about in this book.

On page 59, in Chapter 5: U-175's First Patrol: The Caribbean Theatre, the author states "U-175 had now expanded her torpedo supply inside the boat and had to surface to trasnfer the eight torpedoes from the deck storage containers. This had to be done at night, without lights, and involved six to seven hours of heavy, arduous and dangerous labour."

Any comments?