I had a cool ND lastnight where I was in the sea. I wish it was a LD, have you ever had one where your underwater what was it like?
I did! It didn’t start that way though. I flew over an ocean and swept down into the water, completely submerging myself for a small amount of time.
To my amazement, I could breathe under water.
Yes, I remember several dreams where I was underwater, and I could breathe down there too. One time I was swimming through a sunken ship.
No LD, but I can remember a very long and vivid ND where I did a lot of swimming and the water was amazingly clear. It was perfect.
Ditto. I’ve never had a lucid dream underwater either - come to think of it, I’ve never even seen any water in any of my lucid dreams! They were all inland. But I remember two normal dreams that took place underwater. One was in a lake and series of canals, and the other was in some submerged man-made tunnels. Both were very good. 
I walked on water in my first LD; censored now I just remembered… I was breathing underwater too… (swimming pool)… That was a looong time ago XD
Yes, I’ve had underwaters LD’s and I find it very natural to breathe under water.