Liner replacement over existing liner?

[poconojoe]

Has anyone ever replaced a liner over an existing one while the water was still in there? Would it be a bad thing if a little water were trapped between the old and new liner?
So, what I'm asking is: do I need to completely drain the pond to replace the liner?

 

[addy1]

I would drain the pond and also poke holes in the old liner. If run off/water gets between the two you might end up with a night mare, the old liner filling up with water and pushing up/floating the new liner.

 

[gardengimp]

And dang slippery while working in it. Punching holes in the old liner should drain the water you can not siphon.