Line a cookie sheet with wax paper. Place the caramels and hot water in top of double boiler. Heat over simmering water, stirring often, until caramels are melted.
Use a fork or thick skewer to hold marshmallow; dip into melted caramel and turn to coat entire surface. Roll the marshmallow in the toasted coconut or pecans. Place each on the waxed paper. Work quickly to coat each marshmallow. Stir the caramel mixture occasionally to keep it smooth.
When all are finished, place in a cool place until caramel is firm. Store in a covered container in a cool place.