Unexploded shells in shallow seas

Could shallow seas still contain large numbers of unexploded shells on the seabed?

Yes. Shells that were neither crushed nor rendered inert by corrosion can remain dangerous, particularly when dredging or fishing brings them up.

Unexploded shells can remain on the bottom of shallow seas, including the North Sea and Irish Sea. A shell that has not reached crush depth and still has a surviving detonator presents a particular concern. Corrosion and the condition of the fuze affect whether old ammunition remains dangerous. Dredging and trawling can therefore encounter ordnance long after it was fired or dropped.