Displacer Blub
Working at ManvsMachine I had the chance to discover a new way to create this kind of landscapes just with a plane and the displacer effect.
All you have to do is to create a plane object, then add a displacer effector as a child and play with the layers on the shader parameter. It's worth playing with so many layers to reach complex shapes (some of my shapes have a plain effector as well).