Swimmers who visit Belmont Park this summer might wonder why there is a pool so close to the ocean. Or, they might welcome a dip into an 85-year-old water palace — the Mission Beach Plunge. The place is a rare reminder of the roaring ’20s when the pool was part of millionaire John D. Spreckels’ dream of a special resort. It would also include a dance hall, casino, plunge, roller rink and a roller coaster. He even planned to extend the electric street car route to the beach area. Today, the plunge is part of The Wave House Athletic Club, a health and fitness facility. Guest services manager Chelsea McGovern said the club has been averaging between 700 and 800 people a day. “Of course, that might include 500 of our members, who work out here,” she said. “We have 3,000 members who come here the year-round.” The Wave House, in operation for seven years, includes a restaurant and wave machine. with 45 employees for exercise training and swim instruction. The plunge first opened in May 1925 as the Belmont Park center piece. The 12,000-square-foot pool at the time was the largest salt water pool in the world, holding 400,000 gallons of water. The building was styled after the Spanish Renaissance buildings in San Diego’s Balboa Park and was originally opened as the “Natatorium.” Spreckels used his wealth to build hotels, expand transportation facilities, establish a business district and to develop San Diego’s cultural features. One of those features would be an elaborate sea and bayside resort at Mission Beach. The area was selected in 1922 for an amusement center with access provisions for surf bathing and concessions. Three years later, the Mission Beach Amusement Center, later called Belmont Park, opened to considerable public interest with its tent city, much like that near Spreckels’ Del Coronado Hotel. He never did see the final product of his vision. Other developers took over after his death and brought in many other attractions. Other than the Giant Dipper roller coaster, the Plunge is the only remaining structure to survive from the original park. In 1940, when the salt-water began to damage the filter system, fresh water was brought in. The pool was closed in April 1987 due to not meeting city earthquake and fire requirements. The closure applied to the entire park, which eventually reopened in the summer of 1988.