The 5-inch, 25 caliber Wet Gun on the Main Deck has a stainless steel liner inside the barrel to resist corrosion from seawater. This Gun is designed so that it can be submerged and flooded without harm to the gun.
The barrel is 125 inches long and the diameter of the projectile is 5 inches. The rolling of the submarine’s deck makes a longer barrel of little value as accuracy requires that a gun be held steady while aiming and firing.
“We shall never forget that it was our submarines that held the lines against the enemy while our fleets replaced losses and repaired wounds.” Chester W. Nimitz
Photo Credit: By GordonMakryllos (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons