i have had quite a few dreams of being underwater. and i can breathe underwater in all of them.
supprisingly i have never become lucid when realising i can breathe underwater. each time i wake up i tell myself if it ever happens again you must know you are dreaming and become lucid. but it never does.
most of my dreams undewater include a nice big reef with lots of fish and of course sharks (my favourite animals)
I’ve never gone underwater in an LD, though I have several times in NDs. Usually, though, I’m drowning in them. 
I’m always in a pool, never in an ocean or anything like that (though I wish I was!)
Water is a typical DS for me too, but that doesn’t mean I usually recognize it! 
Yep, I’ve voyaged a bit. Sometimes I can breathe underwater, but once I noticed I just wasn’t breathing at all.
I had a brief dream last night where I was underwater. It was wicked short though. I realized that I was underwater, thought about this post and then became aware that I was breathing. Then I woke up.
I love my underwater dreams… I’ve had a few, and they’ve been filled with the most exotic wildlife and scenery. 
Underwater dreams are great. So far, I’ve never been lucid while underwater, but my NDs involving undersea travel are great fun. Such a strange feeling to breathe water, isn’t it? A lot like breathing through a plugged nose, as a reality check.