[Tim Alphabeaver]

Isn't the claim that water will always magnify objects? That's how the wiki reads to me. Simply providing a case where water magnifies an object isn't enough.

Fill a glass of water and wave it around in front of your face, varying distance between your face, the glass, and the object, and you'll see that water doesn't always magnify objects.

[Tumeni]

The photograph and illustrations are used multiple times.

So what? The context of the photo you posted here, with its two coins, is clearly for the illustration of Activity 3, not 4.

They're not scattered around the document at random

[Tom Bishop]

The photograph and illustrations are used multiple times.

So what? The context of the photo you posted here, with its two coins, is clearly for the illustration of Activity 3, not 4.

They're not scattered around the document at random

It doesn't matter which photo is used. The straw in the water photo is also magnified. The section is clearly describing that looking into water magnifies objects.

p.52:

Put the objects into the pot. Space them out evenly.

• Cover the pot loosely with a piece of plastic wrap.
• Secure the plastic wrap with the rubber band. Gently push the plastic wrap
to make a small dip in it.
• Carefully pour water into the dip.
• Look down into the pot. The water magnifies the objects.

Deep water

Show students that pools and ponds are always deeper than they look. This is because the light rays from the bottom bend as they leave the water. This bending of the light makes the bottom of the pool or pond appear closer than it really is.

Sciencing:

https://sciencing.com/water-magnify-things-4925557.html

Light in Water

Looking from above, an object under water appears larger than it does in air. It's not that the image the light gave our eyes is bigger. It's that the image is actually closer to our eyes, since the light is not passing straight down, but is instead bending relative to the water's surface. Light passing straight down would be perpendicular to the water's surface, like the vertical line on the letter T. A closer image looks bigger--the underwater object is magnified.

Quora:

https://www.quora.com/Why-does-an-object-appear-to-be-bigger-inside-water-when-seen-from-outside-How-does-refraction-work-in-this-case

Q. Why does an object appear to be bigger inside water, when seen from outside? How does refraction work in this case?

A. Objects in water, seen through a flat surface, do appear magnified when the eye is close to the surface.  Anyone who has used a diving mask under water will be aware of this.

[Macarios]

If observed from the thinner medium the object submerged in the thicker medium looks bigger,
it also means that the objet in the thinner medium observed from the thicker medium looks smaller.

If that polar bear was in the air and we are in the water, it would appear smaller.

[spherical]

I can make anything in any transparent medium look larger or smaller, deformed, twisted, bent, inverted, etc, viewed by another transparent medium.
It all depends on the shape of the border between both or all mediums, and the angle of incidence of the photons.

The lack of scientific knowledge about optics in general population, indeed not difficult, leads most of the population to create and believe in popular belief, not exactly facts.  The popular belief is based mostly on "what you see is what you get", this kind of reason lead to several magic tricks, where optical illusion is used plenty.

Optics is a scientific field most unknown and "distorted" in the popular knowledge, even being really easy to grasp and understand.
I believe the great responsible for that is how little it is explored in school, at home and at 99% of the regular jobs.

Several online training optical labs and exercises help to start to understand how things really works:

https://www.newpathonline.com/free-curriculum-resources/virtual_lab/Mirrors_and_Lenses/10/8,9,10,11,12,13,14/1911
https://ricktu288.github.io/ray-optics/simulator/

Very good:
https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html

A pack of simulations:
https://ophysics.com/l.html

This is a very numeric and adjustable, for advanced optics students:
https://arachnoid.com/OpticalRayTracer/

A very simple optics test to find out how much you know:
https://www.proprofs.com/quiz-school/story.php?title=light-practice-test--

This is very good to start to understand optical concepts:
https://www.miniphysics.com/ss-ray-diagrams-for-converging-lens.html

One of the first "wow" about understanding light, image refraction and reflection, is when you compare light with radio frequencies.  On the old AM radio you tune one station and you have a voice, sound, song, etc, it is almost complete, whole, you can be listening to it for hours without losing any bit of information, considering the reception is good and your own language.  On light image, it is like tuning to a thousand different frequency radio stations at the same time, each one transmitting a part of that image, if you see (hear) just one transmission it will be very difficult to grasp about the total final image.  It will be like seen a monkey just observing the violet band of light its body reflects, you will not understand it.  You need more frequencies, more stations, only by seen (hearing) several stations at the same time you will start to grasp the final image.

A simple example of few "radio stations" carrying different part of the final image, based on CMYK filters:


This is why optics field become very important in the late 20th century, when the industry and scientific development realize they could understand better the composition of matter by just tuning few selected of those "radio stations", and observing certain frequencies of light instead of everything at once. Chromatography became popular in the scientific area.  You can burn a piece of anything and observe the gases resulting on the flame and identify almost 100% its chemical composition. You can analyse all signals "transmitted by those hundreds of radios" from the light reflected by a planet and identify most of the gases on its atmosphere.

There are much more under this rug than discussing about a straw inside a cup with water, or the light bent over the ocean moisture denser medium, and the first impression you have, without understanding it deeply.   

And that, it is just studying plain fixed density and optical refraction index of materials, like water, glass, crystals, etc, but now there are materials with gradient index of refraction, creating a total new field of study and work, light can bend in a variable way.

https://en.wikipedia.org/wiki/Gradient-index_optics

Think about this:  You go to a brain neurosurgeon and explain to him about a certain recent headache.  You try to tell him what you think it is, about the skull bone, nerves, veins and arteries, muscles and try to make your medical knowledge become important to him.  The surgeon will keep listening to you, will make a magnetic resonance imagine recording and evaluation, then will prescribe a single aspirin to help dissolve a tinny cloth you have in a non important artery. As a matter of fact, the cloth dissolves by itself and you never had the headache anymore.  Obviously you think your knowledge and talk helped a lot the doctor decision, without your info he would not be able to find and fix your problem.  Do you really think your very superficial and popular distorted knowledge of the human anatomy and works will dramatically change the 30 years of experience and hundreds of surgeries, thousands of analyzed MRIs of such doctor and his team?
 

[stack]

You can also limit the effect of diffraction/magnification through a medium by simply adjusting the aperture. Or in a human's case, the amount of dilation: