Mines are among the biggest hazards facing the U.S. Naval fleet. They can occur suddenly and without provocation, meaning that crews have to be on constant guard of their surroundings. In 1988, the USS Samuel B. Roberts was quite nearly sunk thanks to an Iranian mine in the Persian Gulf. A few years later, the USS Tripoli and USS Princeton suffered significant damage during the first Gulf War.
To cut down mines before they take out our ships, the Avenger class floats in to perform minesweeping missions. One such ship is the USS Sentry.
These ships are built primarily of wood with a coating of glass-reinforced plastic to reduce the ship's magnetic signature and protect it against mine blasts.