In a bowl, whisk the milk with the water, melted butter, and eggs. Mix the flour and salt in another bowl. Whisk the milk mixture into the flour. Strain the batter into a measuring cup and refrigerate for 1 hour.

In a bowl, blend the cream cheese with the butter, lemon zest, shallot, capers, dill, and fish sauce and season with pepper.

Spray a 12-inch nonstick skillet with cooking spray. Heat the skillet over moderate heat. Pour 1/3 cup of the crepe batter into the skillet and swirl the pan to coat it evenly. Cook the crepe until lightly golden on the bottom, about 1 minute. Flip the crepe and cook for about 30 seconds longer. Transfer the crepe to a plate and repeat with the remaining batter.

In a medium bowl, toss the spinach with the olive oil and balsamic vinegar. Fold each crepe in half. Spread about 2 tablespoons of the cream cheese mixture vertically down the center of each crepe. Lay the salmon over the cream cheese. Top with the spinach salad and tomatoes and season with pepper. Fold one side of the crepe over the filling, roll to close and serve.