Abstract-This paper analyzes the extremely low frequency electromagnetic wave excited by a horizontal electric dipole immersed in the sea. Analytical solutions in the air from HED underwater are deduced using a three-layer model. The effect of the sea-air interface is studied along two perpendicular directions. The electric field is inversely proportional to the square of r while the magnetic field is inversely proportional to the cube of r along the interface. By decomposing the total response into direct, up-going and down-going components, contributions of each component are discussed, indicating that interference cancellation effect occurs among the arrival electromagnetic signals from multi-paths at specific offsets and frequencies.