Abstract: An underwater firearm system includes a gun; a sealable plastic bag; a tube; and a plastic material sealing the tube. The sealable plastic bag seals in the firearm and keeps it dry when moved underwater. The sealable plastic bag is configured to enable a shooter to hold the firearm therein placed and pull the trigger, which for example may include a finger cavity that extends through the trigger guard so that a shooter's finger may be inserted into the tubular cavity to engage the trigger. The tube has an inner dimension at least as large as the bore of the gun. The plastic material seals the tube against the inflow of water when the tube is moved underwater. A removable watertight cap optionally fits over the barrel and plastic bag at the muzzle to reseal the sealable plastic bag after having been breached by discharge of the firearm.