A few years ago my 1979 P-30 developed a shallow indentation on the hull's port side under the forward shroud maybe a foot above the waterline and hasn't worsened. It's about 6-8 inches in diameter. It seems to be more visible some times than others perhaps depending on how the light hits it. Recently a second similar indentation has appeared under the aft shroud on the same port side. These locations would seem to coincide with the chain plate locations. Since I believe this is not a cored hull, I'm hoping it's not a moisture issue. Any ideas ? How serious is this ?