I don't know if this is legit or not, but it seems like a lot of doubts are from poor reporting.
He was barely sunburned and didn't die of hypothermia... He also didn't starve to death or die of dehydration.
However, he says that he spent most of the time sitting inside his boat, which was upright. While he mentions bailing water
out, it isn't clear how much of the time it was waterlogged (it might have only been after he initially rolled over)
He mentions catching fish
and drinking rainwater. However, it is also clear that he had food
already on board. This was his home.
I have a vision of this guy just hanging out bored inside his boat and occasionally opening up another can of pork and beans to pass the time. I have no idea what happened, but this reporting is miserable.