Combine the watermelon, tomatoes, cucumber and smoked paprika in the bowl of a food processor or a high speed blender. Pulse until almost smooth. Add the olive oil, vinegar, salt and pepper and pulse until smooth. Taste and adjust the seasoning. Chill the soup for at least an hour or overnight so the flavors meld. Adjust seasoning again before serving. Garnish with cubed watermelon pieces and a drizzle of olive oil. Add a pinch of sea salt and serve chilled.