Chill 2 tall glasses in the freezer for a few minutes so the float stays frosty.
In a small pitcher, whisk together the half-and-half, coconut syrup, and vanilla extract until smooth.
Add ice to the chilled glasses, then divide the orange soda between them.
Slowly pour the cream mixture over the soda in each glass to create a creamy swirl.
Gently add 2 scoops of vanilla ice cream to each glass.
Top with whipped cream, sprinkle with orange zest, and garnish with an orange slice. Serve immediately with straws and spoons.
Notes
Make it dairy-free: Use coconut creamer and non-dairy vanilla ice cream. Boozy twist: Add 1.5 fl oz vanilla vodka or coconut rum per glass. For extra fizz, pour the cream slowly down the side of the glass to avoid overflow.