Fill a shallow plate with coarse sea salt. Moisten the rim of a Margarita glass (or a rocks glass, jar etc.) with a lime wedge then dip into the salt to frost the glass.

Coarsely grate the cucumber then use your hands to squeeze out the juice into the cocktail shaker.

Add all the remaining ingredients and a large handful of ice. Shake until frost forms on the outside of the shaker.

Strain into the prepared glass and decorate with a lime wedge or a strip of cucumber.