I am going to disagree with Esshup just a little bit. I feel it's more about the word warranty. Like eshhup said, there is probably no one that will have a "warranty". However, I feel there are a lot of pond builders that would stand by their work, and if something wasn't right they will come back and fix it. The secret is to find those that have a good reputation and a hand shake in their mind is a commitment. Their charge to do the pond right is usually not a "deal", but they have the know how to do it right and know how much it costs to have to come back and fix something if it isn't done right. I would also think that if the land owner starts telling the builder to do it this way or that way, and if the builder disagrees in the owners approach, I imagine the builder will come back to a "problem" later on and say it's not his fault.