It doesn't take a tsunami...

...as this AP picture shows, with the Ft. Calhoun nuclear power plant in Nebraska now completely surrounded by water as levels continue to rise in the Missouri River.

Following the June-July 1993 flooding along the Missouri River, the NRC published Information Notice 94-27 which revealed that while giving safety assurances to the public during the flooding around the Cooper nuclear power station near Brownville, Nebraska, water was actually coming into the reactor building and rising on safety-related electrical circuits vital to reactor cooling even with the unit in shutdown. Floor drains can become fountains. There is additional concern from rising flood water inundating an on-site auxillary building and the reactor's "spent" fuel storage pool now located on the nuclear  island in our midwest.