Six Flags Hurricane Harbor is Arlington's major seasonal waterpark, set near Six Flags Over Texas and the stadium district. It is not a cultural sight, but in a summer-focused North Texas itinerary it can be a legitimate full-day stop, especially for families building a trip around the theme parks.
The value depends heavily on season, weather, and crowd tolerance. Expect slides, wave pools, lazy rivers, and the usual logistics of lockers, parking, and timed entry. If you are not specifically looking for a waterpark day, Arlington has stronger all-weather sights; if you are, this is the destination-scale option rather than a neighborhood pool.