Going under water, especially at great depths, you can feel one paradoxical thing that is very difficult for our brain to perceive - what a huge world is hidden under water. On land, we get used to seeing our world, we feel it and feel it every day, and it is perceived by us as the most common occurrence. But going down under the water, we discover a new, completely different, unusual and even frightening dimension. And the sea surface, like a portal between these worlds, hides them from each other.