what would a similar object do to earth? would land or water impact make a difference? crazy stuff.
Water strike? Depends.
Very deep water, tsunamis all 'round, saltwater rainstorms for a few hundred miles.
Shallow water? Worst of both worlds. All the impact damage of a land strike, plus all the tsunami damage of a deep water strike. AND as a special bonus, when sea water attempts to flood back into the white hot crater the surrounding thousand miles gets steam cleaned down to bedrock. The rest of the planet gets very hot and humid, and it rains salt water globally...