The idea of a sea-level canal is not new; plans for such a route through Nicaragua predate construction of the Panama Canal itself.
Sandrock, John E.
"School of Naval Command and Staff: A New Isthmian Canal—Key to Hemispheric Progress,"
Naval War College Review: Vol. 18
, Article 2.
Available at: https://digital-commons.usnwc.edu/nwc-review/vol18/iss8/2