Evaluating the effectiveness of tidal wave barriers
The hypothesis holds true: the "artificial mangrove swamp" absorbed the impact of tsunami waves more effectively than the man-made barrier.
Mangrove swamps are normally found along the coast. They are very effective in stopping the onslaught of tsunami waves. One of the first signs of a tsunami is called a drawback. This happens when the sea water recedes very significantly along the shoreline before tsunami waves are unleashed.
Use a larger water tank that has a greater depth.
Vary the gradient of the shore.
About tsunami - http://www.kjc.gov.my/english/education/seismology/whatistsunami.html
Tsunami - http://en.wikipedia.org/wiki/Tsunami#Drawback
Basic safety requirements