[Campbird (OP)]

Since 1969, I have searched for those who have had an experience similar to the one I had with a rainbow.  I have learned that it is scientifically impossible to touch a rainbow, much less pass through one and view it from all angles. Nevertheless, that is what happened to me.
At the time, I was an USAF officer stationed at Fort Yukon, Alaska.  Two companions and I frequently explored the wilderness in a 28 foot, flat bottomed boat on the many tributaries of the Yukon River.  On one occasion, we were about 100 miles north of the Artic Circle on the Black River when we saw a rainbow in the distance.  We thought nothing about it until we got closer and could see that it landed in the middle of the river ahead of us.  We expected it to disappear, as we had basic knowledge of rainbows and knew that we would not be able to actually pass through it. 
As we got closer, we began to realize that we were experiencing something very unusual and strange.  We decided to steer the boat through the rainbow and see if it would disappear as we did it.  The rainbow did not disappear or move as we passed through it.  The colors could be seen on our clothing and belongings.  We judged that the "thickness" of the rainbow was about five feet in the horizontal and about 30 feet in the vertical.  The rainbow terminated in the water and extended into the sky in  a large arc, for what seemed to be several hundred feet.  We continued to navigate around the rainbow and observe it from all sides.  We passed through it several more times before continuing up the river and leaving it behind.
We all agreed that we had experienced something very extraordinary but didn't realize at the time that it was scientifically impossible.  Years later, I felt the need to share the experience with others and posted my story online.  Surely, we were not the only three people in the world that had seen a rainbow from the inside and touched it.
I don't expect the scientific community to believe my story, but it is true.  Not that the status of an individual making such a claim has anything to do with the validity of such a claim, but if you are thinking that I might be someone who would be prone to exaggeration or fabrication, I am not.  I am a retired architect who co-founded a company with 150 employees and offices in four cities.
If you have had a similar experience, I want you to know that you are not alone, and you are not crazy.

[Petrochemicals]

Every time i spray a hosepipe. What was its breadth as the rainbows i have seen that are not by hosepipe, the end of them have no leprechaun, pots of gold and are considerably wider than 5 feet, so i suppose thats down to viewer perspective.

[Campbird (OP)]

The rainbow I experienced was sharply defined with a shape that was narrow (ext. 5' width) and long on the other axis (est. 20' to 40').  It sored into the sky in a large arc.  We circled the rainbow and it never changed shape, color or size.

[Colin2B]

The rainbow did not disappear or move as we passed through it.  The colors could be seen on our clothing and belongings. 

What you are describing sounds like a spraybow. You can get these in the spray from surf, waterfalls, fine rain, or a fine mist from a hosepipe (as @Petrochemicals says). I’ve also seen them with fine dew on grass and fine rain droplets in the air. These can be walked through and seen from different angles. The compressed arc shape suggests the sun was at an acute angle to the plane of the bow.
You don’t say whether there was rain, mist etc, but one possibility is that water vapour rising from the warmer water was freezing to put fine ice crystals in the air which could have the same effect. If the water or ice crystals are very small, the bow can be caused by diffraction in which case the colours are reversed.
Can you say more about the atmospheric conditions eg air temperature, faint mist/haze etc? Did the bow have the same intense colours of the std rainbow or was it fainter or less saturated?

[RD]

Not everything that looks like a rainbow is a rainbow, see ...


https://www.thenakedscientists.com/forum/index.php?topic=18551.0

[Colin2B]

Not everything that looks like a rainbow is a rainbow, see ...

The image @RD posted is typical of the diffraction effect I mentioned. The colours are muted and reversed ie red on the inside. What you describe is a reflection/refraction bow.

I have learned that it is scientifically impossible to touch a rainbow, much less pass through one

Whoever told you this is mistaken. They are talking about the common rainbow where the water droplets are some distance away. With spraybows you can most certainly touch the bow because the moisture in the air is much closer. The type you saw does not need raindrops but can occur with fine particles. Typically they are reported by swimmers, but anyone close to the water surface (where the moisture lies) can see them eg canoeists. I’ve driven through one on a road after a heavy rainstorm where the fine droplets were still in the air, but invisible in the bright sunlight.
The unusual aspect of yours is the high arch - elliptical bow - this most often occurs with dewbows and I’ve seen these on grassy slopes where you can’t see the actual dew until you look very closely at the grass.