Mission Bay was a shallow tidal marsh until the 1940s, when the city dredged it into a recreational lagoon as part of a comprehensive plan for the area. The result is a 4,200-acre aquatic park — the largest man-made aquatic park in the United States — ringed by 27 miles of shoreline, most of it sandy beach, with calm protected water inside and the Pacific ocean outside.
The bay is engineered for recreation: kayak rentals, paddleboard launches, sailing, jet ski rentals, and windsurfing all happen here on the same water simultaneously. The calm water makes it ideal for beginners; the bay is shallow enough throughout that standing and wading is possible in most areas. Fiesta Island at the bay's centre is a natural area with walking trails and one of the few off-leash dog areas in the city.
Mission Bay Park's grassy areas along Crown Point and Vacation Island are used heavily for picnics and family gatherings. SeaWorld sits on the bay's southern shore. The bay views of the downtown skyline and Coronado Bridge from the northern shore are as good as any in the city.