Abandoned naval mines become more likely to explode over time, due to several factors:

• Corrosion: The metal casings of naval mines can corrode over time, weakening the structure of the mine and making it more likely to rupture.
• Leakage: Corrosion can also lead to leakage of the explosive material inside the mine. This can make the mine more sensitive to shock or vibration, and therefore more likely to explode.
• Deterioration of detonators: The detonators in naval mines can also deteriorate over time, making them more likely to explode prematurely.

Many naval mines are designed to self-destruct after a certain period of time. This is to prevent them from becoming a hazard to navigation in the future. However, the self-destruct mechanisms in these mines can also fail over time, making the mines even more dangerous.