Hello there @elmar.evers!
Searching around the community, this issue could boil down to the way UDS and WBO render along each other. Since both cloulds and water use a combination of translucency and depth, the engine can have a hard time picking which one to show from a high position.
I would suggest adjusting the underwater post process settings, change the priority leve here (not the same as Translucency Sort), and make sure its set lower than any other global effects in use. Also, you play around with blend radius value, and the advanced rendering features below.
As for UDS itself, I would check if any depth fog effects are enabled, and adjust the altitude of your clouds. The thread below has an issue, not with an ocean, but still with dissapearing elements:
Yet, for more advanced tips on this asset, you would need to reach it’s creator. The support email on their site is support@ultradynamicsky.com