LONDON, England (CNN) — A sunken galleon, modern-day treasure hunters, a fortune in silver coins and the Spanish navy.

It sounds like the recipe for a great swashbuckling yarn, but is actually the cast and crew of a real-life struggle for millions of dollars worth of lost treasure currently being played out on the high seas.

Rather than cut-throat pirates following maps to mysterious coordinates, these days the search for undiscovered riches beneath the waves is being led by well-funded private companies.

This week a Spanish warship held an American treasure hunting vessel, the Odyssey Explorer at gunpoint, ordering it to return to port in Algeciras, Spain, where it was searched for clues as to the whereabouts of a shipwreck that has uncovered a fortune in treasure.

It was the latest episode in a battle between the salvage vessel’s owners, Odyssey Marine Exploration, and the Spanish authorities, sparked by Odyssey’s recovery of 17 tons of silver Spanish coins worth an estimated $500 million in May this year.