Thank you both very much for your help, I tried to play with the underwater post processing settings, and also manually tried the different volumetric render target modes. But both didn’t change anything in the result. I do however think you’re right it has something to do with the order of translucency. Sometimes, during working in the scene, all of a sudden it looks correct. But after changing any settings in the UDS, it pops back to the way it was.
It not only occurs with the ocean body, I tried to cover the horizon with mountains but it also happens with those meshes. I did also find out it happens only in the far far distance. In the example images below you can see how a mountain mesh correcty intersects with the clouds when its kind of ‘close’ to the camera, but when you move far way from them, the same render issue occurs.
