It’s a lovely story, much of it supported by history, but the suggestion that the ship was carrying treasure is a myth that built up over time, largely as result of the ship being misidentified and confused with other Spanish ships.
It’s now generally accepted that the wreck has been positively identified as the “San Juan de Sicilia”, one of many ships commandeered to reinforce the Spanish Armada. She was originally named the “Brod Martolosi”, based out of Ragusa (modern Dubrovnic) and captained by Luka Ivanov Kinkovic. The Spanish pressed her into service (probably in 1586) and renamed her the “Santa Maria de Gracia y San Juan Bautista” but since she was one of several ships named after St John the Baptist, she became known as the “San Juan de Sicilia” to differentiate her from the others. She then became one of ten ships that formed the “Levant squadron” of the Armada and was captained by Diego Tellez Enr?quez.
The rumours that the wreck was a treasure ship began to spring up soon after the catastrophic sinking, reinforced by stories from the Scottish visitors and hostages held on the ship that the captain (referred to as “Don Diego”) “dined off the finest silver at every meal”. The wreck became known as "the Armada treasure-ship", was mistakenly dubbed the “Florida” (also “Florencia”) and wrongly identified as the “almirante” (flagship) of the Spanish fleet, carrying a treasure of "30,000,000 of money [ducats]". In fact, the fleet’s flagship (Sao Martinho) made it back to Spain, and no ship by the name “Florida” is known to have taken part in the Spanish Armada. There was a ship called the “Duque de Florencia” but she wasn’t the flagship, and also survived the destruction of the Armada.
Over the years, numerous artefacts have been recovered from the wreck such guns, anchors, pewter platters, and medals but nothing that could be called treasure apart from a silver bell. Like all such Spanish ships she would have been carrying her own “pay chest” but it hasn’t been recovered and won’t contain the great riches conjured up by the legend.