Under normal conditions, Shark bodies, which are made of cartilage are not preserved and only the teeth can only be preserved. I searched whether Shark bodies can be preserved in ice and I got this CNN article link about a megamouth shark. I'm guessing this was washed up or something, its preserved in ice at the Smithsonian.
I think sharks could encounter ice or some other preservative material and get trapped, like frozen saltwater, iceberg, or amber. So is there a definitive answer if shark bodies can get preserved in such material? UPDATE I realized frozen salt water would not be a preservative because sharks don't live near the polar seas and ocean, but that does not rule out the possibility of shark catching a current, because warm currents spread out to the poles, and cold water spread out to the equator.