You can see the displacement of the waves without rendering by adding a preview plane to the ocean shader. The preview plane does not appear in renders, but provides interactive feedback as you work in your scene.
Translate and scale it to preview different parts of the ocean.
The preview plane is actually a height field—a plane with the Displacement mapped to the wave height of the Ocean shader. For information on height fields, see the Rendering guide.
For more information on the height field node, see Help > Node and Attribute Reference.
To add a preview patch of ocean