Other finds are mainly rounds that have been dumped due to either misfire or being surplus issue at the end of a ships commission.Some of these are empty but can still have percussion fuses in their base, and others are usually still full of propellant.
Either way great care is required with these rounds as even after what could be 100 years underwater, the propellant will still burn fiercely if ignited,and the fuses can still explode. Even Blackpowder will burn if the sealing on the cartridge was in good condition.
Below is a Nordenfelt 3 pdr. Cartridge case showing a base mounted fuse still in the mouth of the case along with the remains of a projectile long since rotted away. This case is full of “Black powder” propellant which will possibly still burn if allowed to dry out.