Begin by dissolving the blue gelatin according to the package instructions. Allow to cool to room temperature, then refrigerate for about 30 minutes until slightly jiggly.

While the gelatin is chilling, crush your vanilla cookies or graham crackers into fine crumbs. Set aside and distribute the crumbs at the bottom of jars, filling them one-third full.

Carefully pour the cooled gelatin into each jar over the cookie layer, filling about halfway.

Before the gelatin sets completely, gently press in your gummy sea creatures, spacing them for a realistic underwater scene.

Once the gelatin is fully set, add a dollop of whipped cream on top of each terrarium. Optionally, add crushed cookies or small candies.