Preheat the oven to 350 degrees; spray a 9-inch pie plate with nonstick spray.
In a medium bowl, combine the graham cracker crumbs, butter and water with a fork.
Press into the bottom and up the sides of the pie plate. Bake until firm, 3-5 minutes; cool.
In another medium bowl, toss the bananas with the lime juice; reserve 1 cup. Arrange the remaining bananas over the crust.
In a small saucepan, sprinkle the gelatin over the cold water; let stand 2 minutes. Add the sugar; cook over medium-high heat, stirring constantly, until the mixture boils and the gelatin and sugar dissolve, 2-3 minutes.
Remove from the heat; whisk in the yogurt and vanilla.
Pour into the pie plate. Arrange the reserved bananas over the pie; sprinkle with lime zest.
Refrigerate, covered with plastic wrap, until chilled, 2-3 hours.