You will need:
1. Add a few drops of food colouring to the water.
2. Add dry ice piece by piece and allow it to sublimate rapidly.
3. As you add the dry ice you will notice it starting to form clumps at the bottom of the container.
This is where the surrounding water cools down enough to freeze.
4. Keep adding dry ice until a solid clump of ice/dry ice is at the bottom of the container. Within the ice you will no doubt have small white 'frozen bubbles' of carbon dioxide.
5. If you wish, you can add a small squirt of detergent into the mix to trap the bubbles of carbon dioxide leaving the solution.