I highly recommend the new Michael Crichton book "State of Fear". There are some riveting scenes in the book that deal with trying to outrun a tsunami. It's so ironic--I spent Christmas afternoon perched on some rocks, near Big Sur, watching the gray whales migrate and observing the sun as it set into the Pacific. I was closer than I should have been to the water but watched the waves very carefully and wedged myself in to the rocks tight in case the water reached me. The biggest danger would be a powerful rogue wave. I was thinking of the Crichton book and how I would be toast if a tsunami hit the west coast while I was sitting there.
I had no idea that the planet had suffered a massive quake and a tsunami was already building and heading towards the beaches in other parts of the world.
I think the only defense is to gain altitude as quickly as possible by running uphill as fast as you can. If you see the ocean suck all the water of a bay---that's a sign it's time to run like he** because the water will be coming back hard and fast.
I went to the sea cliffs north of Santa Cruz once to witness 20+ footers churned up by a severe winter storm. We chose to stay about 25 yards from the cliff edge (even this was dangerously close). The cliffs were at least 40 feet high at this point. The waves smashed into the cliffs with such force that we could feel the ground shake under our feet. The waves shot straight into the air, and reached 20+ feet above the cliff's edge. To say it was an awesome display would be an understatement.