Use the principle of buoyancy to understand how the U-505 was able to adjust its depth.  Like all submarines, by manipulating a variety of controls, U-boats could change adjust their weight while at sea, enabling them to dive or surface quickly as needed. 

With an 11-foot tall tank of water, take a timed challenge to alter the buoyancy of a cut-away model U-505, including a scaled representation of its ballast tanks.  On the high seas, one mistake might keep a vessel on the surface a split second too long or drop it to crushing depths. Fill the U-boat's ballast tanks with just the right ratio of water and air to reach periscope depth, deep dive and neutral buoyancy—while still compensating for water temperature, saline levels and currents. A plasma screen illustrates an image of your boat out at sea, and signals your success.