We have a crack in our preformed pond.

How do we repair a crack in our preformed pond? It is a heavier black somewhat flexible material, not just cheap plastic.
Thanks for any help.

Doug says here's an article on pond leaks And you're going to be using fibreglass tape and resin to fix the crack once you find it. Do clean and rough up that preformed plastic first though - i.e. follow the directions on the fibreglass kit thoroughly. :-)