OK, I'm not up the maths for a sinusoidal wave, but if you assume triangular waves and...

you have wave crests 20m apart
you have waves 2m from trough to crest
you cross 10km of ground

Your distance through the water is 10198m

At 10m wavelength and 4m height, that goes up to 12806m

If I could do the maths, then a proper sinusoidal wave shape would give even longer distances through the water.