The bubbles are easy; you can make them one by one, resize them then group them as a single stream.   Or, you could create a small long transparent plane, use Scatter and Replicate, or create an eco system and then populate them with spheres that look like bubbles.  There is a bubble mat in the content.

 

You can create a large cube of water above ground plane for your underwater ocean scene.  Move your camera into the water.  There is a tutorial in the Manual for this.

 

Have a spot light with a gel and shine it down on top of the cube of water to get surface light.  You need volumetric lighting to cast rays through the water.

 

That should get your mind working.

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