In a small saucepan, bring the sugar and water to a boil. Cook, stirring until the sugar dissolves, about 1 minute. Remove from heat, let cool a bit, and then stir in the tequila and Triple Sec. Set aside to cool completely (refrigerating is faster).
ASSEMBLE THE WEDGES:
Arrange the watermelon wedges in a single layer in two (9x13-inch) baking dishes.
Pour the cooled simple syrup over the watermelon wedges and refrigerate for at least 45 minutes (longer if you wish).
Remove the watermelon wedges from the syrup, and arrange them on a platter. Squeeze limes over the watermelon and sprinkle with sea salt.
*An alternative way to serve these: you can use a melon scooper to scoop out round balls of watermelon to soak in the syrup, then place two watermelon balls on a toothpick and serve them that way (more like an appetizer).