In a medium saucepan, bring the water to a boil. Add the tapioca pearls and stir gently. Reduce the heat to low and simmer for about 15 minutes, stirring occasionally, until the pearls become translucent.
Remove the saucepan from heat and let the tapioca pearls sit for an additional 10 minutes. Drain and rinse under cold water to stop the cooking process. Set aside.
In a blender, combine the diced mango, coconut milk, sweetened condensed milk, sugar, vanilla extract, and a pinch of salt. Blend until smooth and creamy.
In a large bowl, mix the cooked tapioca pearls with the mango mixture until well combined.
Chill the mixture in the refrigerator for at least 30 minutes to allow the flavors to meld.
Serve in small bowls or cups, garnished with fresh mint leaves if desired.