So, with that in this background, let us today discuss in detail about what the basic equation is and what are the boundary conditions associated with water waves? In fact of when you think of any mathematical modeling for any physical model always, we look into two things. In one of the earlier lecture, I have pointed out that better mathematical; a better model has 3 aspects. If it can be verified experimentally and also, the results can be observed. If three things, the modeling information, modeling results the experimental results and the observational data analysis. If all the three things consider, then we say that is one of the best model.