Here's a quick estimate: The potential energy of the wave will go like mass x gravitational acceleration x height. If the depth (front to back) of the wave is about 1 meter and the height is also about 1 M, then per meter of wave we get

M g h

g = 10 m / s^2;

M = 1 g / cm^3 = 10^6 g / m^3 = 10^3 kg / m^3;

H = 1 m

MGH ~ 10^4 Joules per meter

If a wave comes every 10 seconds —> 10^3 joules / sec, not far from what this person quoted. We need to add to this the kinetic energy, which might double it. Playing with the other parameters we can get close to what the parent quoted.