Unfortunately 'Seeing is Believing' is an accurate statement of how many people form their beliefs.  A belief is valid, however, only if the event is seen and interpreted correctly!

One of my favorite examples of a situation where the idea that "Seeing is Believing" has been used as proof that extraordinary claims are true is the work of Masaru Emoto.  His remarkable claim is that water molecules can be influenced by human thoughts, music and even words taped to bottles to crystallize in specific ways.  He presents pictures of ice crystals to prove this claim: beautiful, symmetric crystals allegedly formed after exposure to beautiful music or uplifting thoughts and words; ugly, misshapen crystals allegedly formed after exposure to negative thoughts and words or heavy metal music.  I discuss my thoughts about the popularity of Emoto's ideas despite their scientific implausibility here.

Seeing, without a good understanding of what your are seeing, is NOT a particularly good process to formulate beliefs. 

Magicians make their living by deception - fooling people into seeing things that are false.  Most good magicians do not claim to have real magical powers, but they are good at deception and can be entertaining.  Customers recognize the presentation as good deception and pay for the privilege of being entertained.

Much of marketing is also deception - designed fool people into seeing things that are false.  Evidence that has been enhanced, misrepresented or completely fabricated is often presented to support marketing claims and to demonstrate the value and performance of a product.  In these instances customers do not recognize marketing presentation as deception and are unwittingly paying for a product that does not perform as advertised.

Back to the alkaline water 'proof'.

Boiled Tap Water	Unboiled Tap Water

My Experiment:
The two bottles on the left demonstrate the results of my experiment.  As you can see I obtained the same results as the Kangen experiment, but I used tap water - I DID NOT use alkaline water.

Let me explain.  Science is all about making predictions (hypotheses) about the causes of natural events and testing those predictions.  One thing that water does very well is dissolve substances that are in contact with it (like oxygen).  Faucets also typically come with a nifty device called an aerator – just the thing for mixing even more oxygen into the water.  From the formula you can see that oxygen in water rust nails. 
4 Fe (solid) + 6 H₂O + 3 O₂ (dissolved gas) → 4 Fe(OH)_{3 (rust)}
Consequently it is not at all surprising that tap water will rust nails in the alkaline water 'experiments'.

After reviewing the formulas for electrolysis and rusting (it has been a long time since college chemistry and my memory of the specifics was a bit rusty), I decided that alkalinity (the OH^– ion) had nothing to do with the rusting process of iron nails in the Kangen experiment.   If you look closely again at the formula for the formation of alkaline water you will notice that hydrogen gas is released at the negative electrode and it bubbles through the water.
2 H₂O (liquid) + 2 e^– → H₂ (gas) + 2 OH^–

I assumed that in the Kangen demonstrations electrolysis had replaced the dissolved oxygen with hydrogen and thus prevent nails from rusting in the alkaline water - no dissolved oxygen = no rusty nails.

My hypothesis was that I could produce the same results by boiling the water, which will also drive the air/oxygen out of solution.  I tried microwaving a bottle of water for a couple of minutes, adding nails and capping it.  The nails promptly rusted - either my hypothesis was wrong or the water had not boiled sufficiently to remove the oxygen. 

I tried again and boiled the water for 20 minutes on the stove then carefully poured it, still hot (risking shattered glass), into a bottle with the nails and capping it immediately - no rust, in fact the hot water seems to have cleaned the nails nicely.

My hypothesis was confirmed, but there are several additional questions that can be asked about this seemingly simple experiment and how well it addresses the original question: Does the lack of significant rust in alkaline water have anything at all to do with the alkalinity?  My experiment did not address pH of the water at all - it simply provided another explanation for the observed results.

It is interesting to note (http://www.public.asu.edu/~jpbirk/qual/qualanal/iron.html) that sodium hydroxide will also produce Fe(OH)₂ and Fe(OH)₃ precipitates from iron that's in dissolved in water.
 Fe²⁺(aq) + 2OH^–(aq) <==> Fe(OH)₂(s)
 Fe³⁺(aq) + 3OH^–(aq) <==> Fe(OH)₃(s)

Since electrolysis of water typically produces sodium hydroxide in addition to the hydrogen gas, if there were any dissolved iron in the alkaline water of the Kangen experiment there should be some rust.  There is, some discoloration (cloudiness) of the water that can be seen in the Kangen experiment images above, so some iron may have dissolved from the nails and reacted with the OH^– ions to produce rust.

I do not have easy access to reagent grade chemicals or a pH meter, but there are several additional experiment that could be performed to see if:
a) adding sodium hydroxide to bring the pH to 9.0 in the boiled-non-oxygen-nail solution will be sufficient to rust the nails which do not have much, if any dissolved iron in the water - some rust would be predicted.
b) adding oxygen to alkaline water to see if that would rust the nails - significant rust would be predicted.
c) adding dissolved iron to alkaline water would be predicted to produce rust in the absence of dissolved oxygen.
d) adding oxygen to the boiled-non-oxygen-nail solution to see if that is sufficient to start the rusting process - significant rust would be predicted.
e) bubbling hydrogen gas through tap water to replace oxygen - this should prevent rust and duplicate results of the Kangen experiments.

Conclusions and observations I would draw from this first experiment would be:

1. The primary cause of rusting in the Kangen experiment is dissolved oxygen in the tap water, not the lack of alkalinity as claimed. 
2. The entire premise of the Kangen argument that alkaline water is an antioxident that protects us from the oxygen dissolved in water and is thus healthy is bogus.  Humans, along with all other animals, depend on oxygen for survival - we are surrounded by oxygen.  We, along with most living organisms, use oxygen to 'burn' fuel (food) and produce energy that our cells need to carry on the functions of life.
3. Oxygen does not ordinarily enter the body through the digestive system, and if it did it would just join the far greater amount of oxygen that is absorbed through the lungs.  The oxygen is then transported to the cells where it oxidizes food to produce energy. 
4. Demonstrating that oxygen in tap water rusts nails is a meaningless experiment.

I would appreciate it if anyone who reads this article and uses the ideas to create experiments to test the theories presented would send me the results of their experiments.  I will publish (or provide links to) any that are performed competently and described clearly.