I purchased a new home and with it came a concrete (I think) pond. This year we decided to drain the pond so we could give it some TLC. That's when I started to realize I had no idea what I was doing and that I should ask some people for opinions.\n\nThe lining of the pond is cracking and flaking off in places (see pictures) and under the lighter blue coat there is a dark blue coat that feels a bit more rubbery when its been sitting in water (once it dries it feels hard). \n\nFirst question, what is all this stuff? I've done some google-fu and YouTube and I don't see a lot of people putting things like this on concrete ponds. It looks like it is similar to stuff used in a swimming pool.\n\nSecond, how worried should I be about the flaking and cracks?\n\nThird, what is the best way to fix this up? I'd prefer not to have to sand the whole thing down if I can avoid it, but I'd rather know sooner than later if that is the only way to fix it up. What kind of material should I be using to patch the areas if patching is all I need to do?\n\nSorry for so many questions, but I feel a bit like a fish out of water here... Oh, speaking of I don't intend to put fish / plants in the pond at this point. Right now I'm just using it as a water feature with a pleasant waterfall when guests are over.\n\nThanks for any pointers!