In a blender, place the mint leaves topped by the watermelon chunks and puree. This may need to be done in batches. Strain the watermelon puree through a wire mesh strainer into a pitcher or large bowl, scraping on the solids to extract as much liquid as possible and to remove any stray seeds.
Puree almonds, garlic, red wine vinegar and salt. Tear the bread into small chunks and place in blender and add about 1 cup of watermelon puree. Puree until smooth, adding olive oil in a slow steady stream and some additional watermelon puree (as much as the blender will hold). Pour this gazpacho mixture into the remaining watermelon puree and stir until thoroughly blended. Refrigerate until ready to serve.