This one sounds most unpleasant for you but there is a positive element to it, Kate.
I also have had a fear of drowning all my life, although I taught swimming lessons as a teenager. However, my latest dreams regarding water are very calm.
What I see is a feeling of maybe not being in control...of some aspect of your life, or in this case, of your death. The worst case scenario does happen but then comes the good part.
You are calmly swimming toward the surface. This is the part where you have control. Because you still have an underlying fear of death itself your mind would not allow you to experience the moment in which you ran out of air.
However, I can tell you that you were making a very good effort to stay alive, and you were calm. Two really good points.
Next time, if you can become lucid enough, simply breathe. You will be able to breathe underwater. I can assure you that in our dreams we can fly AND we can breathe underwater.
There's nothing to fear. I had a dream last year in which I knew it was my last breath. I was just above the water. I felt an incredible calm. That, indeed,is supposed to be the actual experience of drowning, once the person stops struggling and allows themself to breath the water. A calmness descends at that point, and it is not a terrible feeling after that. People can also see what is happening outside their body such as other people trying to save them. This is from numerous near death experiences that people have reported after rafting accidents, etc.
So, see if it repeats in some way. See if you can get lucid. There's really nothing about it to fear there in the water. Not even our own deaths.
love, blink