The Biloxi wade-ins were three protests that occurred on the beaches of Biloxi, Mississippi, between 1959 and 1963. The demonstrations were led by Dr. Gilbert R. Mason, Sr. in an effort to desegregate the beaches of the Mississippi Gulf Coast. Before the beaches were desegregated homeowners claimed the beaches as private property, and although the beaches were built by the Army Corps of Engineers using taxpayer funds, African Americans were restricted to designated areas of the beachfront. The effort to keep the beaches segregated was supported by the Mississippi State Sovereignty Commission.
The first two wade-ins
On May 14, 1959, Gilbert R. Mason, Sr., a physician in Biloxi, went swimming at a local beach with seven other black friends. They were ordered to leave by a city policeman, who told them that "Negroes don't come to the sand beach."  Mason and his compatriot, Murray J. Saucier, Jr., went to the police station to discover what law they had broken. They were told that the police could not show them the law until the next day but that "only the public could use the beach". When they returned to the station on the following day, Biloxi mayor Laz Quave told them "If you go back down there we're going to arrest you. That's all there is to it."  Mason's 1959 demonstration has been called "Mississippi's first public assault on racial barriers in its 15-year civil rights struggle." 
In June 1959, Mason's friend Dr. Felix H. Dunn wrote to the Harrison County Board of Supervisors, asking "What laws, if any, prohibit the use of the beach facilities by Negro citizens?" The Board president's response was that property owners along the beach owned both "the beach and water from the shore line extending out 1500 feet". 
In October 1959 Mason and two other black residents petitioned the board to allow "unrestrained use of the beach". A supervisor asked the group whether they would be satisfied with the use of a segregated portion of the beach and Mason said that they would only be happy with access to "every damn inch of it". 
The "Bloody Wade-in"
The second protest occurred a week later, on April 24, 1960 with 125 gathering before violence erupted in what has become known as "Bloody Sunday"  or "The Bloody Wade-in".  The New York Times called this event "The worst racial riot in Mississippi history." Shots were fired, rocks were thrown, and there was fighting in the streets over the entire weekend. Ten people were shot and a large number were injured in fights. Gilbert Mason was arrested and convicted of disturbing the peace for his role in the protest.  Biloxi police recruited a mob of white citizens and took no action to prevent their violence against protesters.  Mason's office was firebombed later that night. 
On May 17, 1960, the U.S. Justice Department sued the city of Biloxi for denying African-Americans access to the publicly funded beaches. The city delayed the hearing to such an extent that Biloxi black leaders decided to stage another protest in 1963 in order to allow them to file suit in the Harrison County courts. 
The final protest
The final protest occurred on June 23, 1963,  following the assassination of Medgar Evers. Evers had been a popular supporter of the Biloxi Wade-Ins  and had written a letter to Mason proclaiming that "if we are to receive a beating, let's receive it because we have done something, not because we have done nothing".  The protest had been postponed for two weeks to allow participants time to mourn Evers's murder  and protesters placed black flags in the sand in his memory during the demonstration.  Biloxi police arrested 71 protestors, of whom 68 were black. Over 2000 white residents held a counterprotest, in which Gilbert Mason's car was vandalized and finally overturned. 
In May 2009 the state of Mississippi dedicated a historical marker commemorating the 50th anniversary of the first wade-in. Former Mississippi governor William Winter apologized for having stood aside during segregation, saying that
You didn't see this white face [on the beach with Mason] because white people, like me and many others, were intimidated by the massive forces of racial segregation. I have to admit I could not stand up to the pressure for being in public life in Mississippi and come out four-square for the elimination of segregation and for that I apologize today.