Make Panna Cotta:Sprinkle gelatin over water in a small heavy saucepan and let stand 1 minute to soften. Stir in cream and 1/8 tsp salt, then heat gently over medium-low heat, stirring, until gelatin has dissolved. Whisk together yogurt, honey, and vanilla extract, then whisk in cream mixture.Pour mixture into 8 small bowls and chill, covered, until set at least 8 hours.