Yes, it's possible if they are in very cold, low oxygen waters. Fossils of manta rays are fairly common, and there are examples of complete shark fossils preserved by silt and limestone.
Sharks can also be curated using epoxy, formaldehyde, alcohol and other preserving substances. There are famous preserved sharks, one is called Rosie, a great white from Australia, and the other is by Damian Hurst, a tiger shark.