A method for surface-scattered diffraction noise reduction comprising: receiving, by a hardware processor, seismic data associated with a marine region, wherein the marine region includes an ocean bottom, a first zone including water above the ocean bottom, and a second zone including earth subsurface layers below the ocean bottom, wherein the seismic data is generated by using seismic source signals that propagate into the marine region, wherein the marine region reflects the seismic source signals, and wherein the received seismic data includes signals reflected from the earth subsurface layers and surface-scattered noise reflected from the ocean bottom and an ocean surface; determining, by the hardware processor, a water seismic velocity for the first zone; determining, by the hardware processor, bathymetric values of the ocean bottom; based on the determined water seismic velocity and the bathymetric values, determining, by the hardware processor, a two-layer seismic velocity model for the marine region, wherein determining the two-layer seismic velocity model for the marine region comprises using the determined water seismic velocity for the first zone and using a predetermined vertically-constant velocity for the second zone, wherein the predetermined vertically-constant velocity for the second zone has a different velocity value than the determined water seismic velocity for the first zone; calculating, by the hardware processor, the surface-scattered noise by obtaining a solution of a wave equation that models the surface-scattered noise at any spatial position in the marine region, wherein the wave equation models the surface-scattered noise based on the determined two-layer seismic velocity model and wavelet functions of the seismic source signals, and wherein the solution of the wave equation does not include signals reflected from the earth subsurface layers; and determining, by the hardware processor, the signals reflected from the earth subsurface layers by subtracting the surface-scattered noise from the received seismic data. receiving, by a hardware processor, seismic data associated with a marine region, wherein the marine region includes an ocean bottom, a first zone including water above the ocean bottom, and a second zone including earth subsurface layers below the ocean bottom, wherein the seismic data is generated by using seismic source signals that propagate into the marine region, wherein the marine region reflects the seismic source signals, and wherein the received seismic data includes signals reflected from the earth subsurface layers and surface-scattered noise reflected from the ocean bottom and an ocean surface; determining, by the hardware processor, a water seismic velocity for the first zone; determining, by the hardware processor, bathymetric values of the ocean bottom; based on the determined water seismic velocity and the bathymetric values, determining, by the hardware processor, a two-layer seismic velocity model for the marine region, wherein determining the two-layer seismic velocity model for the marine region comprises using the determined water seismic velocity for the first zone and using a predetermined vertically-constant velocity for the second zone, wherein the predetermined vertically-constant velocity for the second zone has a different velocity value than the determined water seismic velocity for the first zone; calculating, by the hardware processor, the surface-scattered noise by obtaining a solution of a wave equation that models the surface-scattered noise at any spatial position in the marine region, wherein the wave equation models the surface-scattered noise based on the determined two-layer seismic velocity model and wavelet functions of the seismic source signals, and wherein the solution of the wave equation does not include signals reflected from the earth subsurface layers; and determining, by the hardware processor, the signals reflected from the earth subsurface layers by subtracting the surface-scattered noise from the received seismic data.