Saw some figures form Steve Munatones on Diana Nyad’s blog.

“The demographic group that is experiencing the greatest percentage of growth is women over the age of 40 – […]

[F]or the first time in history, a major open water swim (defined as an event with over 5,000 competitors) had over 50% female entrants (at the Great Swim in England in 2009). In 2009, 41% of the English Channel swimmers were female – a significant increase from the historical 32% of channel aspirants being female.