This is not 80-million-year-old shark. The viral claim is false.

Claim
Prehistoric 80 million year old shark also known as “the frilled shark” discovered in Awashima, Japan
Rating
Explanation
The scientific name of this frilled shark is Chlamydoselachus anguineus and this video is shared by many social media users with a claim that this is 80-million-year-old shark. Similar posts with nearly identical claims can be seen here, here, here and here.
What’s the truth?
The discovery or spotting of the frilled shark is not a recent phenomenon as claimed by some of the social media posts. A news report uploaded to YouTube in 2007 suggests that this video is at least 15 years old. Similarly, the Reuters also reported this in 2007 which can be read here.
Although the lifespan of Chlamydoselachus anguineus is unknown, an estimate puts it at around 25 years, not 80 million years. The disparity in the lifespan comes due to the fact that they have lived on earth for close to 80 million years and has not undergone systemic changes as part of evolution. The conditions that these species live in did not warrant significant changes since the time of the dinosaurs. According to the National Geographic, “Frilled sharks are often called “living fossils,” because in the 80 million years they’ve lived on Earth, the fish have changed little.”
There seems to be some confusion with the fact that these sharks, as a species, have been around for more than 80 million years without undergoing any big systemic evolutionary changes and its lifespan. In 2017, the shark was spotted near the Portuguese coast and some misunderstood and misquoted its lifespan which includes some big news outlets such as The Independent, The Indian Express, The Daily Express.
Conclusion
A species of shark that has been around in the ocean for more than 80 million years is misunderstood as an individual shark that has been living for over 80 million years which is false.