Previously, the record for the highest number of skip was 40, set by
Kurt Steiner at the Pennsylvania Qualifying Stone Skipping Tournament
on September 14, 2002 (Guinness Book of World Records). In 2007,
however, Guinness confirmed that Russell “Rock Bottom” Byars broke the
record with 51 skips.
Source: http://www.loc.gov/rr/scitech/mysteries/stoneskip.html