Combine the blueberries, water, lemon zest and juice, and Swerve in a saucepan. Bring to a boil over medium-high heat. Lower the temperature and simmer, uncovered, until the blueberries are very soft. Strain the mixture into a large mixing bowl through a fine sieve. Whisk in the half-and-half. Cover with plastic wrap and refrigerate at least 4 hours or overnight.

Pour mixture into an ice cream maker and process according to the manufacturer’s instructions. Scrape the ice cream into a loaf or cake pan, cover, and freeze until firm, about 2 hours. Can be stored in the freezer, covered, for up to a week.