Heat the vinegar in a small saucepan and simmer over medium-low heat until thick, syrupy and reduced to about 1/2 cup, about 20 minutes. Watch carefully to make sure the vinegar doesn't burn. Set aside to cool.
Bring 4 cups water and the jalapenos to a simmer. Remove from the heat and let steep for 15 minutes, then drain, let cool and pour over the watermelon in a bowl.
Before serving, drain the watermelon on paper towels and move onto a platter. Drizzle the strawberry vinegar reduction over and add the feta cheese, mint, parsley and basil. Season with black pepper, if desired.