The Blatant Truth To Waterproof Footwear - There is only one type of footwear is completely waterproof.
What is Waterproof Footwear?
Waterproof boots or shoes mean they can submerge in the water a while and water could not soak into the materials, your feet will stay dry.
Below shows a few water droplets on top of the boots after dipping into the water, which means water cannot get in the footwear and your feet is protected.
However, there are trade-offs for the shoes being waterproof, such as they are usually stiff, lack flexibility and the nonporous materials hold in moisture from sweaty feet, makes your feet feel stuffy in warm weather, and in cold weather, your toes will be even more chilly after sweating.
There is no universal or established standard to measure waterproofness of any items, and hence problems arise when companies try to communicate with their buyers.
Difference Among Waterproof, Water-Resistance & Water-Repellant
Water-Repellant footwear is very likely coated with some form of thin-film nanotechnology on the inside, outside, or both of the item. The term is heavily debated because unpredictable elements that are associate with it and a durable water-repellant is scarce.
Still, the coating renders the boots and the shoes have a better chance of standing up to water than water-resistance footwear but is inferior compares to waterproof footwear.
Water-Resistance shoes keep your feet dry in a light rain drizzle, not a heavy downpour. It offers minimal protection, unless you are going to wear it for jungle exploration or hiking trip to the mountain, it is sufficient for your daily wear or day trekking in your neighbourhood park.
How is Waterproof Made?
The most common method is a layer of waterproof material or membrane bonded to the outer shell of footwear.
The main types of waterproof, also known as WPB fabrics, is considered as two types of membrane. The first one is PU which stands for polyurethane, and the second is an ePTFE membrane or expanded polytetrafluoroethylene.
If you are unfamiliar with the chemistry names, you might hear Gore-Tex from outdoor gear brands as it is the first ePTFE fabrics invented by Bob Gore in 1978.
Bob Gore discovered that if the material has to block water, its pores must be smaller than the water molecules, but larger than water vapour molecules to let the air flows freely.
Below is a video testing the waterproof-ability and breathability of SuperFabric®.
On the other hand, PU coating on fabric has no pores and it also attracts water to the surface, which causing it not performing well in damp and humid environments.
The Most Common Waterproof Materials Use on Footwear
Polyester is unlikely to absorb moisture but is not fully waterproof unless it is coated with PU. It is flammable and burns and melts at the same time when approaching fire.
The disadvantage when making this material as footwear is that it absorbs water and oil. It happens that our body odour is oil-based, binding to the polyester and the smell never vanish after washing.
Nylon, like Polyester, is less breathable and need a layer of coating to withstand water.
However, the smell will not stay long on nylon shoes after washing.
It helps to feel colder when warm, but also the moisture is going to stay longer in your shoes compares to polyester. 
Vinyl can be found in many household items, from vehicles, tents, flooring to clothing and shoes. The material gives the item a glossy-finish and is very waterproof, rigid and flexible.
On the flip side, the rigid material doesn't breathe well and is difficult to stretch if we order the wrong size.
Thermoplastic polyurethane (TPU) is mainly used in outsole (back counter support fixture in ALTAI® Hiking Shoes) as it is soft, flexible and wear and abrasion resistance. It is even suitable for reusable nappies due to its absorbent and comfortable nature.
Rubber and/or polyvinyl chloride (PVC) materials are used to create goloshes/overshoes and jelly shoes. Rubber materials protect against water and are more flexible and provide better traction indoors and outdoors. PVC materials protect against chemical spills and offer good indoor traction on wet floors.
Leather is not waterproof; it is water-resistant. If you step in puddles for some time, the water will eventually get in your leather boots or shoes.
The table below displays the most common waterproof materials used on footwear nowadays with their technology and usage.
Waterproof is Not Permanent and Need Treatment to Restore It
Regardless you are wearing waterproof membrane or coating to protect your feet; those materials will wear off eventually in a few years. To restore the function, you can re-proof your boots or shoes using the spray from time to time (perpetually, in fact).
Below are the recommended products to revive your footwear's water repellency.
Leather Boots:
Synthetic Material (Polyester, Nylon, Vinyl, Rubber, Gore-Tex & SuperFabric®):
Waterproof Comes With Consequences
- In hot conditions, waterproof shoes tend to trap excessive perspiration and body heat. In addition to being uncomfortable, these are ripe conditions for the formation of blisters.
- In prolonged wet conditions, waterproof shoes or boots will eventually be soaked through. External moisture easily enters through the top of the shoe; it can also pass through the seams of the waterproof boots on well-used pairs.
- After getting wet, waterproof shoes dry relatively slow because there is lesser airflow through the shoe to exchange humid interior air with dry external air. No matter what type of footwear you are wearing, while the shoes are drying, feet are confined in a hot and wet environment, which again are favourable conditions for discomfort, maceration, blisters, and the growth of bacteria and fungus.
Luckily our SuperFabric® is breathable and quick-drying at the same time. :) 
Come back to our title, the only type of footwear that can immerse in water for hours while safeguarding your feet from the water...
I think you already know the answer - Rain Boots.
Sources:
Brand, G. "What Kind of Fabric is Waterproof?" Fabrics, Bean Bags R Us, May 17, 2020, /what-kind-of-fabric-is-waterproof/
Gross, J. "Polyester vs. Nylon Clothing for Hiking" LightHeart Gear, April 23, 2018, /polyester-vs-nylon-clothing-for-hiking/
Nadia. "Salomon Climashield vs Gore-Tex: What is the Real Difference?" Off The Grid Gear Hub, May 22, 2017, /salomon-climashield-vs-gore-tex/
Shoaf, R. "Keen.dry vs Gore Tex vs M-Select Dry: What is the Best Waterproof Footwear?" Outdoor Gear, Well Traveled Mile, January 30, 2020, /keen-dry-vs-gore-tex-vs-m-select-dry/
Skurka, A. "Complete failure: I gave “waterproof” Gore-Tex hiking shoes a second chance" Andrew Skurka, August 13, 2016, /waterproof-gore-tex-shoes-second-chance-complete-failure/
Timbrook, R. "Keen Dry vs. Gore-Tex" Expert World Travel, May 1, 2018, /expertworldtravel.com/keen-dry-vs-gore-tex/
“Waterproof Vs. Water-Resistant – What’s The Difference?” Best Walking Shoes Review, Date blog post was published, /waterproof-vs-water-resistant-whats-the-difference/
"WATER-RESISTANT VS WATER-REPELLENT VS WATERPROOF: WHAT’S THE DIFFERENCE?" HZO, /waterresistant-waterrepellent-waterproof-whats-difference/
"What Waterproof Materials are Used in Footwear?" Work, Camping & Hiking Gear, Comfort Work Boots, /what-waterproof-materials-are-used-in-footwear/