The Schnellboot S-31 hit one of the loose mines it was laying around the Grand Harbour of Valletta, and sank. This was during the World War II and the Schnellboot is considered as a World War II wreck. Unfortunately not everyone made it out, 13 of the crew managed to get rescued and 13 of them did not survive. It wasn on the 10th of May of 1942. This had made Schnellboot a war grave.
S-31 wreck lies at around 70 m depth in upright position on the sandy/silty seabed. This is a boat dive for technical divers. The wreck is about 33 m long and 5 m in beam. Schnellboots were made of aluminum frame covered with mahogany planking, and the wooden casing of S-31 has rotted away leaving only the metal frame. Otherwise the WWII wreck still is fully intact with its original weaponry for divers to explore: the three engines, triple propellers and rudders at the stern, twin torpedo-tubes at the bow with torpedoes ready for launching, and the anti-aircraft machine guns still standing.