UPDATE: The Monroe County Sheriff's Office tells us Thomas Swindal died of a cocaine overdose.

On the list of things not to do when you discover a mysterious package full of white powder, snorting the substance is probably near the top of the list.

Unfortunately for 53-year-old Thomas Swindal, he did not heed that advice and died last week after he thought he'd just found a floating kilo of blow, according to the Monroe County Sheriff's Office.

Swindal was fishing with his brother off the shore of Marathon when they found a brick floating in the water they believed to be a package of cocaine, police say.

Swindal's brother told police that Thomas Swindal decided to put the brick on their boat and, when he looked back at his brother a bit later, noticed he had the package open and was snorting it up.

Around 90 minutes later, Swindal began to run around the boat, throwing his cell phone and radio into the water, and then began mangling the engine with random tools to the point that it wouldn't start, according to the cops.

Swindal's brother then threw all the sharp things and the mystery package of powder off the boat before signaling state Fish and Wildlife Conservation Commission officers to rescue them.

Swindal was taken to a Miami hospital and died the next day, police say.

The cops say they believe the package could have possibly been cocaine, but they're waiting for autopsy results to come back to find out.

Meanwhile, the sheriff's office ask that you not salvage bricks of powder from the ocean, and it's probably not a good idea to snort it either.

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