Dreams and visions about a submarine tells you something about the spiritual and emotional way you are in life and how you look at a situation.
Another explanation is that a submarine, reflects your deepest emotions, feelings, experiences, past lives and the womb of life. As it were, you travel through your own soul, source, base in search of ..... or becoming aware of the fact that ... is protected by the universe, god and / or that with which you are connected.
You are looking for a protective floor, new thinking, out of the box. But you can also think of developing as yet unknown powers, properties, experiences and possibilities. Yet another explanation is the reflection of the challenge, trying, learning, understanding, figuring out and everything that has to do with it in life.
Dig a little bit deeper, sometimes you have to go through a particular layer before you get there, where you need to be and / or before you can find the answers you need.
Another explanation is the transition between feet on the ground and new unknown things in life, feminine energy that is clearly present in your life. Water reflects the womb of life, the beginning, the basis, your start, your soul. Without water, there are no chances of new ideas and fertilization of your plans and wishes. The submarine, submarine also tells you something about finding other dimensions, new worlds, spiritual growth and development from your source, your base, life purpose.