[djf]

I'm not sure either!! Does what you say mean that if I have a steel rod, say 5 miles long, and I smack the end of it with a sledge, that the far end doesn't move any faster than the sound wave would get there?

Either way, remember the vectors. The force it would take to displace the water and move it horizontally is almost perpendicular to the force of the object hitting the surface of the water (assuming it came down from directly overhead).

One hell of a mess. Not the kind of experiment I would advocate trying.

[NYFriend]

You're right about the vectors, which would also increase the amount of force directed towards the ocean floor.

As for your steel rod, no it's not limited by the speed of sound, because the force from your hammer blow isn't transmitted entirely as a pressure wave, the rid is a solid. Although, I suppose in your example, assuming the mass of the rod and hammer are the same (huge hammer, tiny rod), and I whacked the rod on my end with the hammer moving at twice the speed of sound, and you were standing on your end, I think what would happen is you'd see the rod move at twice the speed of sound (assume no friction, no inertia, and no bending on the part of the rod), you'd hear the sonic boom created by the rod's movement, then you'd both see and hear the rod vibrate due to the hammer strike (that vibration would move at the speed of sound in steel) and then you'd hear the boom from the hammer breaking the sound barrier and the sound of the hammer strike (which would move through the air at the speed of sound).

Again, I think this is what would happen. I'm not schooled in the hard sciences. Someone here can probably sort us both out.