tsunamis and submarines

This may already have been answered somewhere, if so I apolgize for the redundancy.

A tsunami racing through the ocean, as we’re told, might be hardly noticeable to a ship on the surface. What if a tsunami is in an area and you’re in a submarine under the water? Different story? I’d guess it’s a way different story, but does anyone know for sure?

Well, my WAG would be that if you are close to the epicenter of the earthquake that spawns the tsunami, you’d be buffeted by the pressure wave under the surface.

If however, you are simply dealing with the wave passing by your position nowhere really near the epicenter, it depends on your depth. All water motion due to a wave stops at a depth of 1/2 the wavelength. Now for a tsunami, that a long way down, as the wavelengths are huge. But you must also remember that the amount of motion decreases (linearly?) the farther down you go.