Pond liners

To those looking for a "rubber" pond liner, I would suggest getting the 
material used for rubber-roofing.  Actually it is neoprene.  I have found it 
available in widths up to 50-feet and thicknesses of around 40mil to 75mil.  
This stuff is tough and is designed for prolonged exposure to sunlight.  The 
people I have talked with say it will last at least 30 years in sunlight, so 
it should last a very long time when convered by water.

Best of all, this material is designed to be sold in large volume so the price 
is very reasonable, especially compared with the material sold exclusively for 
ponds (and it's also thicker---the TetraPond material I've seen is 32mil).  
Check your local commercial roofing supply store for the material.