Unfortunately this is a fresh install having just moved over from V4 so includes the HF2.
On further testing I found it is more obvious the lower you get but that also if you pause the sim when you see it afte a few seconds they disappear almost like a texture loading issue. Only difference is the water texture itself is perfect ie not blurred/pixelated, and does not change when the lines disappear. It also isn't effected by EF.
Interesting that there is a post already there on LM. I did a search but must have missed it. I've not had a response from LM on there yet but we'll see.