Flotsam, possibly an expired torpedo (?), with a submarine conning tower (?) behind, near a cliff-lined shore

The identity of the floating object in the foreground is unclear, though of torpedo shape, and whether the object behind is a submarine is equally uncertain. However, some story is concealed here, since the headland shown is probably specific and there is a distant convoy of some sort on the far horizon to the left.

Object Details

ID: PAE0078
Collection: Fine art
Type: Drawing
Display location: Not on display
Creator: Wyllie, William Lionel
Date made: 1914-18 (?)
Credit: National Maritime Museum, Greenwich, London, Caird Collection
Measurements: 250 mm x 352 mm