re: Digging a Pond Questions - Best way for fish and managing snakes?

It an old rice field so I have about 2 feet of topsoil and then a really good clay base underneath. I need a lot of clay to build up my pad bc I have to dig out the topsoil of the pad also and then fill in. I should hold water. I have a creek nearby that will be my overflow. I think if I dig it 8-12 feet deep it should hold water all year.