Bring water to boil in a saucepan, and add the tapioca pearls.
Turn the heat down to medium-low and simmer the tapioca for about 15 minutes, stirring now and then. The tapioca should be soft with only tiny white dots in the center of each pearl.
In a small bowl, whisk the coconut milk, sugar, vanilla and salt. Whisk the coconut mixture into the tapioca. Once it has returned to a simmer, allow it to continue cooking for 5 more minutes and stir it.
Carefully pour or spoon mixture into 4 small bowls or short glass tumblers.
Chill in the fridge until set, at least 1 hour.
For the topping, toast the coconut in a frying pan or in the oven. Sautée the pineapple with the vanilla and Cinnamon until the pineapple softens, about 10 minutes. Add the sugar and rum and simmer for another 10 minutes.
Divide the pineapple mixture onto each pudding, and sprinkle with toasted coconut.