Peel the bananas and place in a medium saucepan. Add the water and then bring to the boil. Turn the heat down and simmer for about 20 minutes.
Break the bananas up with a wooden spoon, fork or masher.
Sprinkle the tapioca into the saucepan while stirring. Add the coconut milk and then simmer over low/medium heat until the tapioca is cooked, about 15 minutes. Stir frequently. Finally, taste the suafa’i. If you like a little more sweetness, then add sugar to taste.
Remove from the heat, leave for about 30 minutes to cool and then serve in a bowl or cup. You can also cool suafa’i completely, and refrigerate it. Once cooled, serve it as a snack or dessert.