Tunnels, seeing loved ones who had passed and the sensation of floating are commonly shared events for those who have had a near death experience, and in those who thought they were dying.
http://www.livescience.com/16019-death-experiences-explained.html
This article comments on the Near Death Experience (NDE) from the medical standpoint. Well written it reports on current research in the medical community on the shared experiences within NDE. It is informative, giving hard facts with the types of chemicals released from areas of the brain and how they can create different perceptions and changes in how one feels, sees, and perceives. Being one of the 3% of the American population who has had and NDE I found the article a great read. Science is doing a good job of finding the various parts of the brain, the chemicals it releases or uses, and the function it performs in relation to our perception of the experiences we are having. It’s great to see research crossing through the veil – helping us to understand the process of dying.