depth charge

noun, an explosive device that detonates under water, esp. for dropping on a submerged submarine, etc. (COD)

“I don’t know, some hatch that should have been shut, or shoot a bomb out, or a depth charge, and they didn’t shoot it right.”

“They were dropping depth charges, and the water was way up, you know, and they said they got them, eh, in the sub. But they used to take and they’d put garbage and all and oil in their torpedo tubes, and then shoot it out.”