The people that found him reported the boat was full of turtle carcasses, @Cruiser, however. Kinda odd that the raw turtle, fish and bird bodies didn’t bother him, but his dead friend’s did. Then again, maybe that’s how he attracted birds.
It seems to me that it would be nearly impossible to to be active enough to prevent your muscles from atrophying, and yet not have sores/sunburn.
Still, we have to give weight to the fact that he was apparently obese at the outset, probably has limited literacy and was a fisherman for 15 years. Possibly he had experienced days, weeks, months alone on the water.
Some of the experts cited just muddy the water. Polynesia to Chili ancient traffic? Well, yes, that’s highly probable, but how likely is it that the natives did that provisioned for a 3 hour tour?