Preheat oven to 325 degrees F (165 degrees C). Place pie shell in a 9-inch pie dish.
Heat caramels and 1/3 cup sweetened condensed milk together in a saucepan over low heat until caramels are melted, 3 to 5 minutes. Spread caramel mixture into the bottom of pie shell.
Heat margarine and chocolate together in a saucepan over low heat until melted and smooth, 3 to 5 minutes. Remove from heat.
Beat eggs, remaining sweetened condensed milk, water, vanilla extract, and salt together in a large bowl until smooth. Stir chocolate mixture into egg mixture; pour over caramel mixture. Top pie with pecans.
Bake in the preheated oven until center of pie is set, about 35 minutes. Cool pie for 1 hour at room temperature. Chill in refrigerator.