Marianne - There are three aspects of your wonderful dream - the sea, the symbol and the blue sky.
Let us start with the sea. Of course we have the ancient sea inside us as the water within us, which is the same level as salt from when life left the ocean. In dreams I see it as representing the ancient source of Life within us - for we are the very tip of the reaching branches of life - so tender. We are too, all the life that has lived and therefore the sea is all the memories - it is what life has done and remembered. It is out of this our growth occurs.
Then the sky is the opposite. The influence of the sea flows upwards in us as growth - the influence of the sky touches us at the head and flows downward. Is influence is to open us to cosmic life - sharing in the life of many. It is the enormous but unlived potential still to make real by living it.
The two immense forces are unknown to most people but are at work in you. You can become aware of them by trying
http://dreamhawk.com/dream-encyclopedia/acting-on-your-dream/#BeingPersonThe two circles are the dual nature of the physical universe and of course living creatures. You are in fact a dual being in many other ways. You have a hidden side of being both female and male; of having a huge heritage of experience gathered from your forebears and the past that you are barely conscious of; and many other aspects of duality you become conscious of as you journey more fully into your unconscious self. In nature the duality is between the male/the sun, and the female/the earth.
The lines dropping down link the sun power, the circles, with female power the ocean. But it is a link between the sea/the unconscious and the sky/the superconscious. And the lines between the opposite circles are a ladder, suggesting a way for you to gain more growth - into the wider awareness. It is like the ladder in which angels descended and ascended between earth and heaven in Jacob's visionary dream. See
http://dreamhawk.com/inner-life/the-unconscious-2/ and
http://dreamhawk.com/inner-life/a-personal-view/They are also the link between the opposites we meet in life. A bridge suggesting a way between the opposites. These shifts, between the dynamic opposites of our nature — tension and relaxation; pain and pleasure; spontaneity and control, are vital for our healthy psychological survival. Factors preventing such mobility are causes for illness and even death. See
http://dreamhawk.com/dream-encyclopedia/healing-action-within-dreams/ and
http://dreamhawk.com/body-and-mind/methods-of-awakening/ Tony