Danger from the Deep
Danger from the Deep (also known as dangerdeep or DftD) is a free Open Source World War II submarine simulator.
Please note: The software uses GPL, but the textures are using a CC-NC-ND-licence. Please don't upload any screen shots of this game to Commons. We got the following screen shots directly from the developers under the Creative Commons Attribution-Share Alike 3.0 Unported License.