Mel Fisher is no relation as far as I know. Arthur's paper is some plentiful in many circles. He says he was involved in 4 mines. I was involved in a few too, but so far the reward is elusive.
Mel was a protege of the legendary Art McKee. We are talking Character here. As in Yosemite Sam. Mckee found gazillions. Mel found good stuff and lawsuits with the guvmint to boot. Lost a son diving. Books on both are written.
With today's sub-bouyant sleds, infrared, sonar acoustic colour sounders, maggotometers/conductivity thingie, and GPS tracking, the treasure cannot hide. Research in Spain/Engalund helps with a spicanole speaking personage. You may also need a Engalund speking person to research there. Funny admiralty records are not as accredited as the Sp. stuff.
We are also seeking some land based treasure, such as the 17 ton 4 corners treasure in NM. That has a story to it. Mined in Mexico and deposited in the States.
EC<:-}