# Translations:Water reverberations/13/en

In our example, the integer T = 3 represents the two-way traveltime parameter in the water layer. The source is a unit impulse at A, which is a point just below the surface. The pulse travels downward in the water and arrives at the water bottom. There, it is reflected. The resulting upgoing pulse at B has value ${\displaystyle {\varepsilon }_{3}}$ and arrives at the water surface C at time 3. The receiver records this upgoing pulse as the primary reflection. However, this upgoing pulse then is reflected downward. In the case of an upcoming incident wave, the water surface has a reflection coefficient of –${\displaystyle {\varepsilon }_{3}}$, so the downgoing pulse at D has the value ${\displaystyle -{\varepsilon }_{0}{\varepsilon }_{3}}$. This downgoing pulse travels downward and is reflected from the water bottom at E. It returns to the surface at F. The receiver records this upgoing pulse as the first multiple reflection, with the value ${\displaystyle {\varepsilon }_{3}\left(-{\varepsilon }_{0}{\varepsilon }_{3}\right)}$ occurring at time 2T = 6. This repeats to produce the second multiple reflection with the value ${\displaystyle {\varepsilon }_{3}{\left(-{\varepsilon }_{0}{\varepsilon }_{3}\right)}^{2}}$ occurring at time 3T = 9. The process keeps repeating itself, each time producing another multiple reflection. Because we omit the shot, we write the trace as