Cornelius:
There is a reference above the one you pointed out:
"Then, in 1969 an American tourist disembarked in Grand Cayman Island (south of Cuba), and to pass the time whilst on holiday, he hired a snorkel, goggles and a pair of flippers and went exploring the shallows of the bay in front of his hotel. Imagine his surprise when on his first time 'out', he discovered a magnificent gold cross, encrusted with diamonds lying in the coral and buried under a few centimetres of sand, and a large gold disc weighing more than a kilo!"
I believe the hotel was the Holiday Inn that Herbo owned. Recall he also had a museum across the street. Perhaps someone in his circle of close friends might give you a lead to the "Santiago".
All the best,
Don....