[colorado tanker]

I heard an interview of an astrophysicist who said a colleague estimated that if this thing landed in an ocean it would raise a 70 meter tsunami. Wouldn't want to be around when something like that came ashore!

[SunkenCiv]

It might generate a tsunami as well, but my uneducated guess is that a lot of the energy would be expressed as vaporization of the water (and the object), leading to powerful storms, widespread blackout, and massive precipitation.