In the 1930s,
gambling ships anchored beyond the regulated three-mile limit, then kept measured from the beach. The ships were popular, and a fleet of ever-larger ships and barges appeared until the State Attorney General recalculated the limit to exclude the bay. The largest ship held the state police off for nine days with
submachine guns in what the newspapers called
The Battle of Santa Monica Bay. Once a major commercial
fishery, Santa Monica Bay's water quality declined drastically in the 20th century as development of
Los Angeles County resulted in large amounts of
sewage and trash-rich storm runoff being dumped into its waters. Through restoration projects mandated by the
Clean Water Act and advocated by groups such as
Heal the Bay and the
Surfrider Foundation, the bay's water quality has improved fairly dramatically from its early-1980s nadir.
Hyperion sewage treatment plant's output is now far cleaner than before. However, during the region's rainy winters, the bay suffers from
algal bloom and other
water pollution-related maladies, periodically forcing most of the famous beaches along its shore to close. On January 13, 1969,
Scandinavian Airlines System Flight 933 crashed into the bay while on approach to
Los Angeles International Airport, killing 15 of the 45 people on board. Five days later on January 18,
United Airlines Flight 266 crashed into the bay after takeoff from the same airport, killing all 38 people on board. In 1990, actor
Wallace Reid Jr. was killed when his
homebuilt plane crashed in the bay amid heavy fog. In 2006, game show host
Peter Tomarken and his wife Kathleen were killed in a plane crash into the bay. They were heading to
San Diego to pick up a cancer patient who needed transportation to UCLA Medical Center for treatment when their airplane crashed. Since 2022,
The Ocean Cleanup has been operating a cleanup system in
Ballona Creek to prevent plastic and other solid waste from leaking into the bay. ==Communities and settlements==