Are waves affected by an under-water barrier? Given a wave propagating at the surface of still water towards a barrier that is below the surface, but at a distance that is of the order of the dimensions of the wave (such as depicted in the scheme below). 
How will the course of the wave be affected ?


*

*Will it be blind to it and pursue its course unaffected ?

*Will it only partially pursue and a part of it will bounce back ?

*Something else ?


<
       wave
       /~~~         
      /~~~~\  ->    
 ~~~~/~~~~~~`~~~~~~~~~~~~~~~~~~~~~~~~ water surface
                      ____  
                     |    |   
                     |    |  
 ____________________|    |__________  
                     barrier

 A: Ocean surface waves that are said to 'feel' bottom are known as shallow water waves which are categorically differentiated from deep water waves according to wavelength and depth, and which are not as affected by the depth of the sea floor. 
Ocean surface waves are a movement of energy, not a bulk forward motion of water but do result in local circular orbits of the water particles. With depth the circular orbits flatten into elliptical orbits and eventually vanish, and it's at this depth obstacles will no longer influence surface wave motion. For obstacles that do intrude into this space, the circular or elliptical motions are disturbed and energy is dissipated towards the upper water layers, building up wave height. IN very shallow water the build up can get high enough that the wave can no longer sustain its shape and you have a breaking wave.
The property that actually leads to the loss of energy from obstacles is the viscosity of the water, the ability for layers of water to flow over one another.
