Is there any obligation to turn over treasure you find yourself? And why?
There is when you take $12 million from investors:
> A total of 161 investors had given Thompson $12.7m (£9.4m) to find the ship on the understanding that they would see returns on their investment.
Both the criminal and civil contempt arose from his refusal to abide court orders from the civil suit.[1]
[1] https://www.justice.gov/usao-sdoh/pr/treasure-hunter-sentenc...
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If investors gave you $12.7 million to fund your expedition, you have an obligation to split the treasure as you promised.