Twelve Seconds to Live - Douglas Reeman (epub)

World War II novel.
The mine is an impartial killer, and a lethal challenge to any volunteer in the Special Countermeasures of the Royal Navy.
They are brave, lonely men with something to prove or nothing left to lose. Lieutenant-Commander David Masters, haunted by a split second glimpse of the mine that destroyed his first and only command, H.M. Submarine Tornado, now defuses ‘the beast’ on land and teaches the same deadly science to others who too often die in the attempt.
Lieutenant Chris Foley, minelaying off an enemy coast in ML366, rolls on an uneasy sea with a release bracket sheared and a live mine jammed, and hears the menacing growl of approaching E-boats.
And Sub-Lieutenant Michael Lincoln, hailed as a hero, dreads exposure as a coward even more than the unexpected booby-trap, or the gentle whirr of the activated fuse marking the last twelve seconds of his life.