First, make the garnish for the rim. Combine the salt, sugar, dessicated coconut and lime zest on a shallow plate. Dampen the rim of a margarita glass and dip into the mixture. Chill the glass until needed.

Pour the tequila, lime juice and rum into a cocktail shaker and add a handful of ice. Shake until the outside of the shaker feels ice-cold.

Drop a few ice cubes into the prepared glass, then strain in the drink.