Line 15x10x1-inch baking pan with foil, extending foil over sides of pan; grease foil. In Dutch oven or 4-quart saucepan, combine sugar, butter and evaporated milk; cook over medium heat until sugar is dissolved, stirring frequently. Bring to a full boil, stirring constantly. Without stirring, boil 5 to 6 minutes over medium heat or until candy thermometer registers 234°F. Remove saucepan from heat.
Add marshmallows, chocolate chips, sweet chocolate and unsweetened chocolate; stir until all chocolate is melted. Stir in vanilla and 1/2 cup of the pecans. Quickly spread mixture in greased foil-lined pan.
In medium saucepan, cook caramels and water over low heat until melted, stirring frequently. Drizzle melted caramels evenly over fudge. Sprinkle remaining pecans over caramel. Cool 2 hours.
Use foil to lift fudge from pan; remove foil. Cut into 1-inch squares.