Assuming you're referring to the clipping border in the horizon - That waterplane has walls on its sides that have a certain material making it look 'infinite', but it's not particularly tall as for the reasons Labeled mentioned, it doesn't need to be because isometric. It's clipping because of particular settings in the atmosphere that is used only draws that far. You could edit the atmosphere to increase the far distance, but you'd still just see a blue "wall" in the distance. The only solution I could think of would be to make a dome with a skyplane material and plug it over Fort Joy in its entirety.
