Happens on all texture packs so it's not the texture pack's fault. Basically at 0 Anisotropic filtering the horizon looks normal but when you start cranking it up It all goes weird. I have included pictures of what I mean at AF 0, 4, 8 and 16. As you can see the effect increases with The Anisotropic Filtering. I also included a picture of what happens when looking at the sea with this effect.