In a small bowl, sprinkle the gelatin over the cold water and let it sit for about 5 minutes to bloom.
In a medium saucepan, combine the coconut milk, heavy cream, sugar, and salt. Heat over medium heat, stirring occasionally, until the sugar is dissolved and the mixture is warm but not boiling.
Remove the saucepan from heat and stir in the bloomed gelatin until fully dissolved. Add the vanilla extract and mix well.
Divide the mixture evenly into serving cups or ramekins and refrigerate for at least 4 hours, or until set.
Once the panna cotta is set, top each serving with the mango puree. You can blend the mango until smooth or leave it slightly chunky, depending on your preference.
Serve chilled and enjoy!