What's in the ocean; what was once in the ocean, and what has always been there has long been a point of discussion. But recently, I took a deeper dive for this profile because I found this so interesting. According to previous researchers, 1.7k years ago a humungous city was swept away by a huge tsunami leaving an entire civilization.
The initial research excursions for lost cities and ancient things had originally begun in 2010. But in 2017, researchers found quite the discovery of a city deep underwater that consisted of streets; monuments, and other usual city stuff.
According to Science Alert, the event/tsunami occurred on 21 July 365 AD.