Tip the sea salt and lime zest onto a saucer and stir to combine. Dip the rims of four margarita glasses in water, then in the lime salt, twisting to coat. Set aside.

Tip the lime juice, pineapple chunks, tequila and triple sec into a blender and blitz until smooth. Pour into glasses and serve immediately. (If the mixture is very thick, leave to stand for a few minutes to loosen.)