Steel Hull Issues

I have been in the coatings biz for 25 years. If you are referring to the blisters below the green tape line, it is adhesion problems and osmotic blisters. Most likely cause is poor surface prep and poor adhesion to the layer below. It could also be poorly/impoper cured paint causing water permeability, if it is a two component paint system. Like a bad mix of epoxy/hardner?? Has it lost complete adhesion to the surface or is it lost adhesion between the layers? hard to tell much more without examining the surface and looking at the backside of the layer of paint that is loose.