Combine grapefruit juice, agave nectar, tequila, lime juice, saline solution and a scoop of Ice into a mixing glass.
Cap, then shake vigorously 20X, until chilled.
Remove cap and add soda water.
Prepare glass by rubbing a lime wedge in a 2" wide rectangle shape halfway down the side of a glass and sprinkling with kosher salt. Refer to photo.
Add 2nd scoop of ice to collins glass. Strain drink over the ice.
Strain drink over the Ice.
Garnish with halved grapefruit quarter-moon on side of rim as shown in photo.
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