K - Class Submarine.
K-Class Submarines were a class of steam-propelled submarines for the Royal navy designed in 1913. Intended as large, fast vessels with the endurance and speed to operate with the Grand Fleet they gained notoriety and the nickname of the Kalalmity class for being involved in many accidents. Of the 18 built, none were lost to enemy action, but six were sunk, with significant loss of life, in accidents. Only one ever engaged an enemy vessel, K-7 hitting a U Boat amidships, though the torpedo failed to explode with what has been described as typical "K" luck; K-7 escaped retaliation by steaming away at speed.