I was not one of those kids who couldn't differentiate imagination from reality. I didn't have much of a wild imagination as a kid, in fact I was quite the critical thinker. I was brought up in religious surroundings and was already questioning religious doctrine that would stump the religious administration at my school.
I assure you it was not an imagination or dream. It was a real life experience. I also have a proven sharp memory of my earliest years that shocks my parents.
I have had numerous 'out-of-body' experiences, paranormal events of various kinds, some quite extreme . Also, after some visualisation practice, spontaneous visualisation/astral travel experiences. My dharma practice began when I was around 15, when I began meditation, chanting and experiments with hypnosis and various forms of trance.
I have already mentioned the flying dreams and the way the mind can lose track of inner and outer reality. I once woke from a trance state and found myself lying on the ground in Africa, during a tribal celebration. I passed out and awoke in my previous location.
There have been some occasions involving astral travel which included very strong evidence of much more than just imagination (i.e. detailed drawings and descriptions of events).
I mention all this to inform you that I am not unaware of or biased against the notion of sidhhis and what is called 'paranormal'.
Without an external witness, there is no way of telling what occurs in the province of the individual mind, and what occurs in the shared concensus reality, the physical world.
Your evidence that you physically floated exists only in your mind. That is significant to note and remain aware of.
I have also been involved in life-threatening accidents, on a motorbike and in a truck, and on both occasions subjective experience of time was hugely altered. A period of one second can be experienced as a complex sequence of events of apparently longer duration. Our perceptions of time and space can alter dramatically under the right conditions (especially if our life depends on it).
Your assertion that you know you physically floated because it seems that way from memory needs to be questioned. Why are you prepared to believe that explanation rather than the much more likely explanation that it was a mental event ?
Is it because you now have a vested interest in believing that explanation - it reinforces a preferred belief about your perceived world being 'mind only' for example ?
The fact is, you have no evidence that your body floated. You have a memory which says it floated. My experiences have taught me that such experiences seem totally real. The only difference between an exceptionally vivid dream and objective reality is that objective reality can be verified. The assertion that "I was not one of those kids who couldn't differentiate imagination from reality" does not constitute a water-tight guarantee that this was not a case of exactly that.
Just to make that last point clearer -
if you subscribe at all to the notion that individuality and the external world is some kind of illusion or perceptual error (and generally buddhists do ...) then you are also acknowledging that in most every moment of your life you can't differentiate imagination from reality. So there is that to consider.
In my opinion, some cultures tend to not differentiate between vivid 'astral' experiences (for want of a better word), and physical reality. The Tibetans for example. Autobiographies and biographies from Tibet often include descriptions of miaculous events which are treated as real. In the jungles of south America there are (or were) tribes whose whole lives involve magic and witchcraft played out as personal power struggles, all of which is considered objectively real by the participants. But it all occurs in the context of drug-assisted trance.
Regarding the quotes from Buddha and others - you have no way of knowing whether the levitation or walking on water referred to is meant to be subjective or objective. What we do know is that dharana, dhyana and creative imagination can produce 'as if real' experiences. I can attest to that.
If you read "The Life of Marpa" (Shamballa), you will find a reference to Marpa's students observing him transforming physically in front of them. (I have also observed this with a lama). Marpa explains to the students that the visions are a result of the combination of their samaya bond and the teachers purity. Consider that carefully.
So in summary, you really cannot say with certainty that your experience was objectively real, and not a function of creative intelligence. There is simply no way you can verify that. Did anyone see you floating ?
You can, if you choose, develop visualisation to the point of utterly realistic experiences. This is of some value in educating the mind about its capacities. But to insist that such an experience is objectively real is an assertion of ego, and will find no external confirmation.
Do you want to have this experience because it will prove something you have chosen to believe ? My experience tells me that I can experience anything as-if-real. But what does that actually prove ?
I highlighted your assertion "
I assure you it was not an imagination or dream", because that is significant. You have already decided the event was objectively real
without first proving to yourself that such experiences can be generated routinely by the mind.
Having said all that, I would recommend that you master visualisation to the point of as-if-real. It is very educational.