If someone had looked out the window and mashed the E-Stop on the generators before the wave hit them, they could have probably gotten them back online relatively quickly.
Hydro-locking diesels renders them scrap iron.
There has apparently been a lot of damage seen in the plant that must have been from the earthquake. The earth acceleration exceeded the rating for quite a few of the reactors, spent fuel pools and turbines. So you have to expect some damage.