Pre-heat oven to 300 degrees.
Place cubed bread in a bowl and toss with 2 Tbsp olive oil and salt. Lay bread cubes on a baking sheet in a single layer and bake for about 15 minutes, until bread is crispy. Let cool.
Place watermelon, cucumber, red onion, jalapeño, feta cheese, and mint in a large bowl. Add in cooled bread cubes and toss until combined.
Drizzle remaining 2 Tbsp olive oil, lime juice, and pepper over salad and toss again to combine.