The underwater is a postprocess effect that adds those effects (distortion, fog and wet lens) to the current scene color when you are below the water surface. The underwater effect is not related to any of the ocean materials (so you have following the video with the wrong material, I am sure I told which one). When you are underwater what you need to do is to not add the effects to the current scene color and instead let it with original color and for that you need a mask (1 will keep the effect, 0 will use default scene color) which is what I try to explain in the first video. There is a video at my YouTube channel which I explain exactly how the underwater effects are setup and explain how it works, maybe it is a pre-knowledge for you to completely understand what I have shown in the 1st video above.