“The fact is that in some ports in the world possession isn’t, as the saying goes, nine tenths of the law,” added Mr. Dragonette. “It is the law.”

Ship Raiders and Port Pirates

Port scams are as old as shipping itself and seasoned repo men can identify them by name. “Unexpected complications”: a shipyard makes repairs without permission, then sends the owner an astronomical bill, often for more than the value of the ship, hoping to force its forfeiture. “Barratry”: buying off crews, sometimes paying more than a year’s wages to leave a ship’s keys and walk away. “A docking play”: a shipowner defaults on his mortgage, but is in cahoots with a marina, which charges the repossessor hyperinflated docking fees. “I swam out to it one night and took the boat back,” said Steve Salem, a repo man in Sarasota, Fla., recalling one such case in the Abacos, a chain of islands in the Bahamas, in 2012.

Mr. Lindsay described a “classic shakedown” case he handled in 2011 in Guinea in West Africa where a ship was being fraudulently detained with a $50 million fine for less than $10,000 in damage to a dock. “They fly you in, you find the right official, and negotiate him back to Planet Earth,” Mr. Lindsay said.

Stolen boats — about 5,000 were taken in the United States in 2014 — are often relocated to “unfriendly jurisdictions,” where local governments are sometimes less sympathetic to American owners and more susceptible to bribes, the repo men said.

Mr. Meacham, the Florida-based repo man, said he was once sent to Havana to retrieve a stolen American-owned megayacht being used by a hotel there. Chartering the vessel into international waters, he then told the Cuban captain: Come with us to the United States or take a lifeboat back to shore. The captain chose the former.