In late 2015 the U.S. Navy revealed that it was training its submarine crews to deliver, while submerged, a Cold War era naval mine design. This is the Mk67 SLMM (Submarine Launched Mobile Mine). The Mk67 looks like a torpedo and up to a point it is. The 750 kg (1,600 pound) Mk67 (based on the 1950s era Mk-37 torpedo) is launched from a submarine and can travel over ten kilometers to a pre-programmed location then sink to depths of up to 180 meters and activate its warhead, which is a multi-sensor naval mine. This weapon appeared in the 1980s and has not been mentioned much by the navy since the Cold War ended in 1991. But with China and Russia reviving the Cold War the Americans apparently thought it necessary to issue some reminders.
Another type of torpedo based mine is the U.S. Mk60 CAPTOR. This is a one ton moored mine containing a Mk46 lightweight torpedo. Maximum operating depth is 900 meters and effective range (of the Mk46) is seven kilometers.
CAPTOR was developed to provide a quickly deployed (by air) minefield that could cover a very large area. The mine is equipped with a powerful acoustic sensor and is supposed to be able to detect subs at a range of several kilometers. Once detection is confirmed and the course of the target plotted, the torpedo is released to home in and destroy the sub. CAPTOR can also be delivered by submarine.