agree with @danny
it's incredible complicated
you'd think it's standard geometry (x, y, z) for the planes but it's a bit more complicated than that.
also it doesn't list what all the integers means.
i fiddled with shorelines.dat and haven't really looked into seeing if i screwed that up.
i believe dkt70 made a water.dat file. not sure how he did it though.
couldn't be arsed to fiddle with it personally.