The UC70 was a small U-boat, just 417 tons and 49 metres long. The armament included an 88-millimetre gun, 2 forward facing torpedo tubes, 1 aft facing torpedo tube and 6 mine-laying tubes loaded with 18 mines. On 28 August 1918 the UC70 was caught on the surface by a patrolling seaplane and bombed, with the destroyer Ouse following up with a depth charge attack.
The first thing I noticed was one of the mine laying tubes. There are six of these in total running vertically through the forward end of the hull. They look like a line of circular manholes with lips rising about 20 centimetres above the surface of the hull. In dock, mines would be loaded in from above, three to a tube. Once in enemy waters the mines would be released from the corresponding openings in the bottom of the hull.
Turning forwards, a vertical shaft with a solid looking cog on the end projects from the top of the hull. This may have been the drive for an anchor winch, or perhaps part of the mechanism for controlling the bow planes.
The robust inner hull is intact, but the outer hull is broken and absent in many places. The front of the inner hull is slightly domed. Forward of this would have been a streamlined bow. All that remains now is a shaft with the skeleton of a hydroplane on either end resting on the seabed. There is no sign of the actual torpedo tubes. Maybe they were salvaged for their high non-ferrous metal content.
Coming back along the port side of the hull, the remains of the ballast tanks start just about level with the fourth mine laying tube. The ribs of the ballast tank are mostly intact, but the plates have rotted through or even fallen clear in several places making it easy to look inside.
Aft of the last mine laying tube is an open hatch. I didn't fancy doing any more than poking my head in, but nothing is visible below. It is hard to imagine a crew of 28 living inside a tube 3 metres wide and less than 50 metres long, most of which is filled with machinery.
Next comes the 88-millimetre gun, still nicely aligned with the hull and presumably locked in its travelling position.
Behind the gun is a section of mast that used to house the search periscope, then twisted plates where the conning tower has collapsed to port. At the top of the conning tower is a hollow mast with the broken attack periscope retracted inside it.
Further back on the hull the aft hatch is also open, looking in slightly better condition than the forward hatch.
At the stern missing plates on the upper side reveal an arrangement of pipes and levers that would have controlled the rudder and rear hydroplanes, and launched the single rear facing torpedo.
There is not a fantastic amount of marine life, but I found the UC70 to be incredibly interesting from an engineering point of view. A submarine in a state of partial undress, with lots of interesting bits of mechanism sticking out.