Bring 1 cup water to a boil.
 
Hollow out the inside of each lime using a paring knife and a melon baller. (Reserve the lime pieces in a plastic food storage bag, freeze and use for a frozen margarita!)

 
In a large measuring cup or a mixing bowl with a spout, combine boiling water, Jell-O, remaining ½ cup water and vodka. Whisk until well-combined, about 1 minute.
 
Place each hollowed out lime half cut-side up in a muffin tin. Fill each lime half to the top with Jell-O mixture and sprinkle 6-8 chia seeds in each one. Place the muffin tin in the refrigerator for at least 4 hours.
 
Remove from the refrigerator and flip them over onto a cutting board, Jell-O-side down. Using a very sharp knife, slice them in half lengthwise, to make a tiny Jell-O filled "watermelon." Garnish with a few chia seeds and serve.