Some Ekranoplans (like the Lun mentioned in the article) have the ability to fly above the ground effect zone, though less efficiently.
If rogue waves (or other rough sea) can be spotted far enough ahead, the plane could increase altitude over brief rough spots, settling back on to its ground effect cushion once calmer waters were reached.
Because it's travelling so much faster than surface waves, the lidar (or whatever scanning system) would only have to consider a relatively narrow field of view in front of the craft.
If rogue waves (or other rough sea) can be spotted far enough ahead, the plane could increase altitude over brief rough spots, settling back on to its ground effect cushion once calmer waters were reached.
Because it's travelling so much faster than surface waves, the lidar (or whatever scanning system) would only have to consider a relatively narrow field of view in front of the craft.