IIRC, the original plan was to build a sea level canal across Nicaragua. It was 86ed when Nicaragua issued postage stamps commemorating a huge volcanic eruption near the proposed rout.
Opponents of this route sent letters to every congress critter and made a point of calling attention to the stamp.
(They neglected to mention that the eruption happened thousands of years ago)...
My granddaughter lives in Costa Ricathey are very upset about this and realize that because they have no army, they are going to have to depend upon the kindness of others to stop the Nicaraguans.
As a side note, Nicaraguans are despised by Ticos. If someone is living like a bum or commits petty crime, they are automatically Nicaraguans.
I have read that there are all kinds of problems that go along with the building of a sea-level canal. One is that the tides of the Caribbean and the Pacific are different thus causing a current in the canal. Another problem is Pacific flora and fauna being introduced into the Atlantic and vice versa. Doubt if Venezuela, Iran and Nicaragua are going to issue an environmental impact study.