Odd shadow rendering on Water

To anyone that can help:

I’m seeing two strange artefacts when dealing with the Water Body Ocean. They both seem to be linked to the dynamic shadow cast my my directional light and only show up on the surface of the water body.

The first is a massive sharp black rectangle (indicated by the red box in the first image) that shifts based on camera position and angle of my directional sun light. There is no object up there casting this, just a Sky Atmosphere.

The second is the poor quality of the shadows from static meshes on the surface of the water that I can’t seem to adjust. Again, the shadows are fine when cast on other geometry.

I’m pretty new to Unreal, though not rendering in general, so any help would be massively appreciated! Thanks