I may have posted about these two awhile back in a similar thread.
"Savage Shore" Life and death with Nicaragua's last shark hunters by Edward Marriott.
http://www.amazon.com/Savage-Shore-D.../dp/0805055568

"Tycoon's War" by Stephen Dando-Collins. Cornelius Vanderbilt vs. William Walker for control of Nicaragua.
http://www.amazon.com/Tycoons-War-Co.../dp/0306816075