Place the rice in the insert of the slow cooker.

Stir together half-and-half, coconut milk, and sugar in a large, heavy saucepan. Place over medium-high heat and cook, stirring, until the mixture is very warm and the sugar has dissolved. Pour the mixture over the rice, stir well, and then cover and cook on LOW for 5 hours OR on HIGH for 3 hours. The pudding will bubble and the rice will be very soft. Turn the cooker off and let the pudding sit for 30 minutes before serving.