Tsunami generation mechanisms emerge as questionable due to its massive destructive potential. Indeed, scientists and engineers are attempting to minimize the excessive hazardous impact of tsunami. In this context, the major causes of the tsunami are required to plan specific defence coastal structures. In this sense, the deep details and comprehensive perception of tsunami generation mechanisms are required. This chapter is devoted to explicate the different factors that can generate a tsunami. Further, this chapter will answer the question as to why are tsunamis not seen at sea or from the air?