You will need to have access to a bath; if you do not, you could use a shower if you find you can relax and meditate whilst showering. An alternative, although I have never tried it, is to just use a bowl of water and wash your chakra points with it. You will need some salt to add to the bath/shower/water, and four crystals, preferably blue, or any that make you think of the sea. I also have a Nammu 'stone' which is a hag stone I found (a stone with a natural hole in it) that I drew in blue pen some waves, and wrote the name 'Nammu' on it - with the hole, I can wear it as a necklace if I ever need to take the primordial energy you will feel during this meditation with me. I also listen to a YouTube recording of the sound of waves crashing, to help set the scene.
Place the crystals at the four corners of your bath, or just somewhere you can see them. Run the bath, start the music if you're using any, and add some of the salt to the bath, to represent the salty waters of the oceans. As the bath is running, kneel before it with your fingertips touching the surface of the water, and start trying to connect with Nammu. Think about the element of water, and how if it wasn't for this element nothing would be able to survive - about two thirds of the human body alone is made up from water, with our blood being 90% water. It is an integral part of our existence.
Once the bath has run, invoke Nammu and state your intent. For example;
"I invoke the great primordial energy that is Nammu. I pray, be with me now and help me understand your presence and power".
Now you are ready to climb into the bath. Submerge yourself as much as possible in the water, feeling it wash over you.
Close your eyes and prepare to meditate. See the world and the people in it, as if you were a bird hovering above the city streets; see people running around on their way to work, headphones in, people sat at coffee shops chatting or staring at their phones, large glass building, cars and busses driving past. Now cast your mind back; she a time before mobile phones and the internet, when cars were less abundant, people wore different dress. Keep casting your mind back, through the Victorian ages, the middle ages, Vikings, Romans, ancient Celts, and eventually Neanderthal hunter-gatherers. Make sure you see the world around you change, from this built up, concrete jungle to the wilderness that once prevailed.
Go even further back; before humans evolved, the variety of animals that filled the earth, back further to dinosaurs and great beasts. Now even further, when the first animals were growing legs and clambering to land.
Cast your mind to the ocean, where all life started. See the land decreasing, becoming bare, turning to lava and sinking back down into the underwater volcanoes where it is believed that eruptions caused the land mass we call Earth. Now there is just water - carry on, until every little microorganism is yet to grow, and there is nothing but the watery abyss of Nammu.
Feel yourself in the water. You have no difficulty staying afloat, it takes no effort on your part, for you are at one with the waves, and you move with the primordial energy as it's waves gently crash to and fro. You are not just at one with the primordial energy - you are the primordial energy.
Feel this energy of creation, from where all life sprung. Remember, Nammu made the decision to create humanity and you are a child of those first humans created. Why did she create us? What is your purpose? Is there any purpose?
When you feel ready, say softly:
"I am at one with the primordial energy - I am the primordial energy, the primordial abyss from where all life evolved. I am a child of Nammu. Nammu, please help me find my path and be the person you intended me to be. May I forever have and feel the primordial energy running through me. So mote it be".
When performing this meditation I feel a deep sense of peace, and belonging. A sense of purpose, at least, the purpose that I believe Nammu has put me/us here for; she may have chosen a different path for you!
Whilst Nammu is generally referred to as a female deity, I have to admit, when meditating on this primordial energy I don't associate it with any gender, just as I don't associate the energy as being good or bad, light or dark, it just is. Just as, despite Nammu being a female deity, I don't 'see' her in the same way I see other deities as physical embodiment's, I just feel the energy - wild, untameable, permanent and everywhere all at once. It really is a powerful meditation if done right, if you really connect with that energy, and is a great way of reconnecting with yourself and the divine if you are feeling out of sorts or have been going through a rough time.