Long-distance swimmer Diana Nyad has discovered dry land. Talking at Symphony Hall as part of Lesley University’s speakers series, Nyad said she’s organizing a series of long-distance fund-raising walks, including one from Boston to New York City. That would be something new for the 60-something Nyad, who in 2013 became the first person to swim from Cuba to Florida without a shark cage. Pointing to one of her heroes in the audience, Boston Marathon race director Dave McGillivray, Nyad said she hopes her walks will raise money for survivors of the Marathon bombing.