Labadee in Haiti has the longest over-water zip line in the world: Dragon’s Breath Flight Line. It’s quite high, and you end up going quite fast. The zoom on my camera may obscure just exactly how high and long the zip line is, so here are the numbers: it is 2,600 feet long and 500 feet high. You end up reaching speeds of 40 to 50 miles per hour! You can read the detailed account here.