Allied depth charges like this one were designed to attack and destroy submerged U-Boats.

Filled with high explosives and dropped or launched from a ship, depth charges sank and exploded at a pre-set depth. A direct hit could destroy a U-Boat, and misses might cause damage, forcing the submarine to the surface. The "Type G" depth charge, smaller and less powerful than many others, was used by small Royal Canadian Navy vessels, including motor launches, drifters, and patrol boats.

Depth Charge, "Type G"
CWM 19390002-455