White gazpacho has a smoother, more sophisticated taste than pink.
Soak bread in ice water for 10 minutes. Remove crust and discard; squeeze out water from bread.
Puree the bread, almonds, and garlic in a blender or food processor. With the machine on, add the olive oil drop by drop until it emulsifies, then in a trickle to finish. Add the lemon juice, vinegar, salt, and pepper.
Transfer to a serving bowl, and whisk in the water until gazpacho has the consistency of heavy cream. Add half the grapes; chill for 1 hour before serving. Halve remaining grapes and use for garnish.