For the lemon vinaigrette: Combine the olive oil, honey, mustard, salt, shallots, lemon zest and juice and black pepper to taste in a bowl and whisk until combined.
For the watermelon salad: Slice the watermelon in half and use a scooper to scoop out watermelon balls. Put the watermelon balls in a large bowl and add the watercress, tomatoes, mint, feta and pine nuts. Add the lemon vinaigrette and gently toss to combine.
With a large spoon, scrape any remaining flesh from the watermelon halves to create hollow bowls. Add the tossed salad to the watermelon bowls and serve.