What happens when a submarine is caught in the chaotic waves? Are these fortresses safe from the towering waves? Or are some dangers also lurking beneath the surface?

A submarine that's submerged deep in the ocean is comparatively safer from a Tsunami. However, the safe word doesn't imply invulnerability. Tsunamis create an immense force that can still pose risks. U.S. Coast Guard and NOAA advise that during a tsunami, vessels should avoid attempting to escape on the surface—instead, if possible, vessels should move to deeper waters

Anything near the surface of water is vulnerable to damage in a tsunami. It can lift and hurl several tonnes of steel, potentially destroying the system. In shallow water, the violent currents and density fluctuations caused by a tsunami can create internal waves. These can rob a submarine of buoyancy and send it plummeting abruptly.

The Lituya Bay, Alaska, on July 9, 1958, was the largest tsunami ever recorded, with a magnitude 7.8–8.3 earthquake that triggered a massive landslide. It generated a staggering 524 meters, approximately 1,720 feet long waves. The K-278 Komsomolets was designed to operate at 1,250 m depth; it is one of the deepest submarines to ever exist. At its designed depth, it is far beyond the reach of Lituya Bay or any other Tsunami.