They don't do well in open ocean which is why only saw them in Caspian Sea. My understanding is that they need to fly a certain distance above the waves to keep

They don't do well in open ocean which is why only saw them in Caspian Sea. My understanding is that they need to fly a certain distance above the waves to keep from hitting them. When the waves are big, this pushes them close to ground effect limit. My guess is that they would be okay for confined seas like Mediterranean. Or uses where they didn't need to keep to schedule.