How to create a seamlessly tileable ocean modifier and textures?

I have created a set up in which an orthographic camera is looking down onto a plane with two displacement modifiers mapped to two empties that move across to the other two edges to create a seamless water effect with an Ocean modifier below these two displacement modifiers. But when I render all of the images from frame 1 to 100 and compile them in GIMP to form an animation map, the image has seams in the animation tiles when it plays in game after I specify the parameters like Animated and Tiles. Why does the Ocean Modifier do that? I need it to create a seamlessly tileable pattern.

Also, I know this may be off-topic, but how on earth can I get Blenders procedural textures like Voronoi to be seamless and animate seamlessly without the use of nodes to make it compatible with the plane that has the normal map colouring node material? Voronoi would make AWESOME lava and viral/bacterial animation maps!

EDIT: The ocean modifier is NOT animated, the Time is always at 0 to avoid interference. The empties as mentioned above do the work.