Place a 9x5-inch loaf pan in the freezer to chill. In a large mixing bowl, whip the cold heavy cream with an electric mixer on medium-high speed until stiff peaks form, about 3-4 minutes.
In a separate bowl, whisk together the sweetened condensed milk, vanilla extract, and salt until smooth and well combined.
Gently fold the whipped cream into the condensed milk mixture in three additions using a rubber spatula. Use broad, sweeping motions from the bottom up to maintain the airiness without deflating the cream.
In a small bowl, stir together the cherry preserves, lemon juice, and water until loosened and pourable but not completely smooth — you want some fruit pieces visible.
Pour half of the cream base into the chilled loaf pan and spread evenly. Drizzle half of the cherry mixture over the top in random lines.
Add the remaining cream base, then drizzle the rest of the cherry mixture on top. Use a butter knife or skewer to gently swirl through the layers in a figure-eight pattern 3-4 times — resist over-mixing.
Cover the pan tightly with plastic wrap pressed directly against the surface, then add a layer of aluminum foil. Freeze for at least 6 hours or overnight until firm.
Before scooping, let the ice cream sit at room temperature for 5-8 minutes to soften slightly. Use a warm ice cream scoop for the smoothest, most beautiful curls.
