In a small village, there is a well-known shallow lake that has a gradual slope as it extends deeper into the water. Imagine one sunny afternoon, Lakpa and Marisol decide to wade into the lake from opposite ends, which are roughly the same initial depth. They both step in simultaneously, maintaining a steady pace, walking straight towards one another. As Lakpa and Marisol wade deeper into the water, at first only their feet disappear below the water's surface, then gradually their legs. At some point, they will only be able to see each other from their torsos upward as the water reaches their respective waistlines. The question revolves around what happens when Lakpa, who is taller than Marisol, and Marisol, who is shorter, reach the point where the water is exactly at Marisol's chin level. What parts of Lakpa are still visible to Marisol at this point? Additionally, if there's a small floating ball halfway between them, what could each person perceive about the ball's location in relation to the water's surface?
When the water reaches Marisol's chin level, given that Lakpa is taller, more of his body would still be visible above the water compared to Marisol. Depending on the exact height difference, it is likely that the water level is somewhere between Lakpa's chest and waist. Therefore, from the perspective of Marisol, she should be able to see from Lakpa's waist or chest up to his head. 

Regarding the floating ball halfway between them, both Lakpa and Marisol would be able to see the ball floating on the water's surface. However, their perceptions would be different due to their height and the level of water around them. For Marisol, the ball might appear to be sitting almost at her eye level because she is nearly submerged up to her chin. Contrastingly, for Lakpa, the ball would appear lower relative to his line of sight, as it would be floating at a level closer to his waist or chest. Since both Lakpa and Marisol are experiencing the water at different heights on their bodies, the ball's perceived position against the horizon would differ for them both, higher for Marisol and lower for Lakpa.