I have a simple shader with a water texure and I'd like to make it semi transparent. Using Blender Internal engine, you can do this just by setting the alpha value on the shader. Is there a way to do something similar in cycles?
It depends on the nodes used to make the material. The latest “Principled” has a transmission slider that controls transparency. In cycles that is all you need; with eeVee you also need to enable that feature.