Submarine M2 was one of 3 M-Class submarines. M2 was outfitted with a small hanger which could fit a small biplane that could be launched from the deck after its wings were unfolded.

On the 26. January 1932 Submarine M2 was out on a training exercise. The last transmission received was at 10:11 reporting that they would perform a dive at 10:30.

The merchant ship Tynesider, would later witness the submarine diving stern first into the water.

After reaching port and not realizing the significance of this, the captain casually asked the harbourmaster if it was normal for submarines to dive backwards. It was not.

After the wreckage was found 8 days later, it was discovered that the hangar doors were open with the aircraft still inside.

It is believed that either the crew opened the hangar doors too soon while there was still water on deck or that the stern hydroplanes failed, which would have caused the stern to move downward, allowing water to enter through the open hangar doors.

Interestingly, the M-Class of submarine, is a refit of the notorious K-Class of submarine. Which was known for being incredibly uncomfortable and unsafe. Out of 18 built, 6 would be lost during accidents. Only one K-Class submarine would ever engage an enemy, hitting a submarine amidships but it’s torpedo failed to detonate.

Several K-Class submarines would also partake in the infamous Battle of May Island. An accident where a series of collisions caused the sinking of 2 and the damaging of 4 K-Class submarines as well as damage to one scout cruiser.