Preheat the oven to 180 degrees celcius (350 Farenheit)Cut the watermelon int slices, removing the rind and seeds. Cut the flesh into cubes, and put them in the fridge to chill while you prepare the croutons.
Cut the baguette into roughly sized squares. Lay them out evenly on a parchment lined baking sheet and drizzle with olive oil. Sprinkle the minced garlic and sea salt over the croutons and bake for 15 minutes, or until crunchy and nicely browned.
While the croutons are baking, make the dressing by combining the olive oil and the balsamic vinegar.
Spread the croutons out on a serving platter, and lay the watermelon cubes on top. Crumble the feta cheese over the top. Finish by adding the olives and balsamic dressing. Garnish with freshly torn mint.