The Cross Florida Barge Canal was intended to connect the west coast of the state with the east coast, thereby allowing merchant vessels to move from one side to the other without having to circle around South Florida. This map shows where the canal was planned, and the parts that were actually constructed. Courtesy: Florida Memory
The Ocklawaha River is a major north-flowing river that feeds into the St. Johns River. It was damed as part of the Cross-Florida Barge Canal Project, but the project was ultimately deauthorized. The dam, Kirkpatrick Dam, did stay, though, and controversy continues as some want the river restored and others want the dam and the reservoir it created maintained.
This is the web site of the short documentary of the story. Available here are additional information, materials and resources.