Pond liner

The pond liner has shifted a bit, probably when it got pushed out with rising ground water in a storm. It's not the normal butyl, but looks like a black version of the cheap tarpaulins. This material, though, is very strong and difficult to cut, let alone tear. It is largely covered all over, but the exposed bits remain strong.
I needed to increase the height on one side, and it had become the low point. Using bathroom silicon sealant, I applied 2 stripes to the back of it, and stuck a new piece on. Then once that had gone off, I put a small strip on the front, again with 2 strips of silicon. The silicon doesn't stick and peals easily. I left that to cure and left it in that position. It has a log to cover the edge and protect it from the sun (south facing edge)
The liner was not nice and flat and had a few U shapes in it. The job was fine on the large flat areas, but a bit variable around the curved bits. A few weeks on and it is water tight enough not to notice the level drop.