WASHINGTON (AP) — The massive superyacht Dilbar stretches one-and-a-half football fields in length, about as long as a World War I dreadnought. It boasts two helipads, berths for more than 130 people and a 25-meter swimming pool long enough to accommodate another whole superyacht.

Dilbar was launched in 2016 at a reported cost of more than $648 million. Five years on, its purported owner, the Kremlin-aligned Russian oligarch Alisher Usmanov, was already dissatisfied and sent the vessel to a German shipyard last fall for a retrofit reportedly costing another couple hundred million dollars.

That...