In a large bowl, whisk together dry ingredients: flour through salt.
Using a wooden spoon, form a small whole in the middle of the dry ingredients. Whisk together eggs, yogurt and vanilla then stir to combine with the dry ingredients.
Pour in seltzer water and gently whisk until evenly incorporated - lumps are ok!
Fold in blueberries using a rubber spatula.
Pour batter into pre-heated waffle maker and cook according to manufacturer's instructions until golden brown.
Notes
Seltzer water is the secret to crispy waffles on the outside but milk makes equally delicious waffles.