Yes, Mel Fisher found the Atocha in 1984. The Atocha was a Spanish ship, part of a "treasure fleet" heading back to Spain with silver and gold from the new world when it was lost in a hurricane in 1622. Fisher searched for many years before finding "the mother load", and actually lost his oldest son and wife in the process when one of their boats capsized. The Atocha was found off of the coast of Florida and some estimates value the cargo at over $400 million. When Fisher died he had a net worth of around $100 million.

This discover actually led to quite a bit of controversy and eventual legislation. At the time, historic shipwrecks in the state of Florida could be salvaged under permit from the state, but 25% of the artifacts had to be turned over to the state for conservation and study. Fisher and his company sued the state, essentially arguing that under maritime law abandoned vessels can be claimed entirely by those who find them. This case (Florida Department of State v. Treasure Salvors Inc.) was escalated all the way to the Supreme Court which ruled in favor of Fisher and awarded him ownership over all of the loot. This was very scary to archaeologists, who worried that more shipwrecks would be privately looted without study. This led to the passing of the Abandoned Shipwreck Act in 1988, which is federal legislation that makes all abandoned historic shipwrecks in state waters the property and responsibility of the state.