“All these people that talk about the Essequibo have never been there,” said Charles Brewer-Carías, a Venezuelan outdoorsman and explorer.

Mr. Brewer-Carías was a youth minister in 1981 when he led a group of about fifty young Venezuelans on a secret excursion over the border and into the Guyanese jungle, planting Venezuelan flags as they went.

He also flew over Guyana in a small plane to map strategic facilities, such as airstrips. At the time he hoped to incite his government to invade. (It got him fired instead.) He started out thinking that the area was an empty jungle, but came to find it was occupied by Guyanese people, towns, farms and mines.

He says that Venezuela should accept the status quo and emphasize friendly relations.

“It is impossible to take away land from a country that has developed it,” Mr. Brewer-Carías said. “We are so given to magical things that we think we will get it and get its oil wells and gold mines.”

On a dock along the Essequibo River, in a town called Parika, Mike Prince, 61, a Guyanese Army veteran, sat watching passengers boarding boats for Bartica.

“I would re-enlist just to chase these sons of back to where they came from,” he said, genteelly omitting an obscene word. It was, he said, all about the oil.

“Greed,” he added, “is a terrible thing.”