The largest sailing regatta of a single class was achieved by 1,055 participants during an event organised by Fraglia Vela Riva (Italy), in Riva Del Garda, Italy, on 6 April 2012.
The sailing boat for the record was the Optimist, a small, single-handed
sailing dinghy intended for use by children up to the age of 15.
Youngsters aged from the age of 9 to14 years old, coming from 27
different countries took place in the regatta. Naturally Italy has the
largest representation with 332 entrants followed by Germany with 235
and Denmark 69. Others have come from as far away as Australia, Bermuda
and The U.S. with 22 participants.
Source: Guiness Book of Records