Add raspberries and water to a food processor; process until smooth.

Press mixture through a sieve and discard solids. Add sugar, vanilla, and lemon juice to raspberry puree, and stir to combine.

Freeze according to ice cream maker's instructions. Then transfer to a freezable container.

Freeze 2 to 4 hours for a firmer consistency.

To make floats, place 1 to 2 scoops sorbet into a glass. Top with champagne. Garnish with raspberries.