On our lotty, by 'wor shed', we have a well established pond for the local frogs 'n' wotnot. I had suspected that the original liner had a leak in it, so I went to the nearby 'highly priced' garden centre and like the last of the big spenders, decided that a new liner was the easier and quickest option. So, £49.95 lighter, we flapped the new liner into and over the old one, having made the pond a wee bittie deeper, by about 150mm, or, 15 cms, or 6", or 0.5 of a foot. After getting it all re-filled with some of the original muck, slime and pond plants, it has settled down into a much nicer looking stretch of water. Not olympic but enough for the toddler pollywogs in the early spring.
Good 'ere, innit !