According to Official Guinness Records,
The largest gathering of pirates was achieved by 14,231 participants at an event organised by Roger Crouch and The Town of Hastings (United Kingdom) on Pelham Beach, Hastings, East Sussex, United Kingdom, on 22 July 2012.
The enclosed area of Pelham beach had 17 entrances and 2 exits, each monitored by 2 clickers, and overseen by 2 independent witnesses in addition to the Adjudicator.
For a complete list of 2012 records, please visit 2012 Guinness Records in United Kingdom.