Here is a little known treasure in the Los Angeles beach area
to try out this summer, The Seaside Lagoon. 
The Seaside Lagoon opens for public use beginning May 23, 2009 and is
open daily through
September 4, then weekends of September 5-6, only.
Situated on the southwest corner of Harbor
Drive and Portofino Way in Redondo Beach's King Harbor,
the Lagoon operates from 10:00 a.m.
to 5:45 p.m. daily throughout the summer months.
The large saltwater lagoon, offers trained
lifeguard supervision.
Besides swimming, the Lagoon offers a large sand area for sunbathing,
children's play equipment, snack bar facilities provided by Ruby's Restaurant ,
 and volleyball courts.
There is also a grassed area and luau shelter for day and evening events.

The Seaside Lagoon is a salt water facility. Water for seaside lagoon comes from the other side of the breakwater, at about 50 feet deep, travels to the near by steam generating plant where they use it to cool the turbines. The water then travels under the street in large pipes to the Seaside Lagoon where it is chlorinated when entering the lagoon and de-chlorinated when leaving the lagoon back into the harbor. The Seaside Lagoon has approximately 1.5 million gallons of water and has a flow through rate of approximately 200,000 gallons per hour.

Thanks to reader Gaby for the tip!