In a tranquil village bordered by a placid lake, two friends, Kehinde and Takashi, decide to spend a leisurely afternoon by the water. The lake is known for its clear waters and gentle slope that slowly descends into greater depths. The weather is calm, with a slight breeze occasionally disturbing the surface of the water, creating small ripples. The sun is high in the sky, casting a brilliant light that is reflected off the water onto the surroundings. Along the bank, trees provide sporadic patches of shade where the friends initially take refuge from the heat.

Kehinde, whose curiosity often leads to spontaneous adventures, proposes a game to test their spatial reasoning skills. The challenge is to estimate each other's height in relation to certain landmarks on their bodies when partly submerged in water. They scan the shore and notice that a group of reeds grows at varying heights along the water's edge. Moving towards the lake, they decide to use the tallest reed, which reaches up to Kehinde's shoulder when he is standing next to it on dry land, as a point of reference.

The friends wade into the water side by side at a leisurely pace, their feet sinking slightly into the soft bed of the lake. As they venture further in, the water level rises uniformly on both of them. They both notice that their perceptions of distances and sizes of objects around them start to change as the refractive properties of the water alter the appearance of items submerged in the water.

Kehinde, who is slightly taller than Takashi, watches as the water reaches his mid-torso; from his vantage point, he observes that the water has risen just above Takashi's waist. Takashi, on the other hand, sees the water encroaching upon Kehinde's lower chest. They continue to gaze at their surroundings, noting how the other fixed objects such as trees on the shore appear slightly displaced from their original positions when they looked at them from the bank.

Given this scenario, the question arises: When both friends look down at their own and each other's submerged legs, how do they perceive the length of the legs in comparison to when they were on dry land? And what happens to their perception of the length of the reed that was at shoulder height to Kehinde when they look at it from their submerged positions? Furthermore, if they both submerge completely up to their necks, what change would they see in the perceived height of each other, and how would the above-water parts of their bodies appear in relation to the actual proportions? Provide a brief response.
When Kehinde and Takashi look down at their own legs and at each other's submerged legs, they find that the legs appear shorter than they actually are. This is due to the refraction of light as it passes from water to air. Light rays bend away from the normal line as they move into a less dense medium, causing the submerged parts of their bodies to look closer to the surface than they actually are. The effect of this optical illusion is that their legs appear not only shorter but also magnified, with a somewhat distorted shape in comparison to what they expect on land.

The reed that stood shoulder-high to Kehinde when observed from their submerged positions will appear to have a bend or a displaced segment where the part of the reed meets the water's surface. This is because the submerged part of the reed will seem to shift towards them while the portion above the water remains unmoved. This creates the visual perception of a disjoint in the continuity of the reed's straight form, making it appear bent.

Once Kehinde and Takashi are submerged up to their necks, their perception of height will be heavily altered. Kehinde's slightly greater height will be less discernible to Takashi. To each other, their exposed heads and necks would seem disproportionately smaller in relation to their bodies, as these parts are not affected by the water's magnifying effect. Furthermore, to an outside observer on the shore, their heads would look unusually small compared to the distorted, magnified size of their submerged torsos.

Additionally, from their neck-deep perspective in the water, their view of the surroundings will drastically change. The above-water portions of their bodies will seem normal, while the landscape and people on the bank will appear to be situated higher than expected due to the light refraction at the air-water interface. They will also have a wider field of view for the submerged sections, creating a peculiar and broadened perspective of the underwater environment. However, the parts of their bodies and of objects that are still above water will maintain their regular size and appearance, creating a stark contrast between the submerged and unsubmerged parts of their world.