The Hunting Mine Mk 25 is a recoverable, inert-loaded shape. It is planted in the water by surface craft solely to help mine countermeasures personnel develop their mine hunting skills and techniques.
The original Mk 25 Mine was designed and used during WWII. Employing a magnetic induction influence firing mechanism, the Mk 25 was a 2000-pound mine containing an explosive charge of 1200 pounds of HBX-1
Here is a great video of the Old Mk. 25 mine is action: Allied aircraft lay mines in Pacific Theater during World War II.
The mine weighs approximately 2,000 pounds with its tail cover. The mine does not contain explosives or target detecting/actuating mechanisms and, therefore, is ballasted internally with concrete to maintain its necessary negative buoyancy and bottom stability. The mine’s case is painted either white with orange stripes or orange with white stripes.