If a 50 to 100 meter object strikes the ocean, what is the primary threat described?
Massive tsunamis capable of devastating coastlines.
Objects in the size range of 50 to 100 meters are categorized as presenting a serious regional threat. The specific consequence of impact depends heavily on the location of contact. If such an object impacts the ocean, which covers the majority of the planet, the immediate and far-reaching danger involves the generation of massive tsunamis. These waves possess the capacity to sweep inland and devastate coastlines across an entire ocean basin, posing a significant danger even thousands of miles away from the precise point of impact, necessitating immediate evacuation from low-lying coastal areas.

#Videos
What If A Giant Asteroid Hit Earth Tomorrow? | FULL DOCUMENTARY
How to Survive an Asteroid Impact - YouTube