One of my characters is a sleep-walker. The most important scene where her somnabulism is involved is when she goes out of her house in the middle of a storm and walks into the sea. I don't know if it's realistic that she doesn't wake up with the storm and the water. Also, most of the information I've found is too impersonal, I'd like to really understand it from her point of view, what she feels and remember. If any of your followers is somnambulist I wish they could contribute too. Thank you!!
People have driven long distances while “sleepwalking”, so I suppose it would be possible. Personal experience: My uncle sleepwalked outside during a thunderstorm to get the mail at midnight. I just found out a comedian once jumped out of his hotel window while asleep - if people will put themselves in life-threatening situations, it stands to reason walking into an ocean while under the same influence wouldn’t be too difficult. Look here, here, and here for sleepwalking experiences.