Stick grenades

When the German U-boat finds the Powell family and Hesperus after La Bourgogne’s sinking, this is what the German Navy officer uses to destroy their lifeboat.

Stielhandgranate is the German term for "stick hand grenade." Stick grenades were a common World War I and World War II German grenade design.

They have a long wooden handle, a pull cord to activate the grenade, and a cylindrical “potato masher” explosive end. The pull cord ignited the fuse, causing the grenade to explode less than five seconds later.