Black Tie Beach is an annual event staged by Improv Everywhere in August. A diverse group of people of all ages spend a day at the beach wearing black tie attire. Participants enter the beach separately in small grounds and proceed to sunbathe, play games, and swim in the ocean, all in formal wear. Participants are instructed to find cheap tuxedos and ball gowns at thrift stores for the occasion.
Here is a history of the project: