As Winnie follows Angus to the pond, she feels brave again with the thought that the man in the yellow suit might rescue her. She enjoys the sound of her boots on the rowboat and listens to a bullfrog across the pond. Angus climbs in with her and pushes the boat out across the pond. Softly, he says that this is feeding time for the creatures in the pond. He says that all around them, creatures are living, growing, and changing. Even though the pond looks the same every day, it isn't, because it's always moving. Eventually, it'll reach the ocean.
Remember that Winnie isn't entirely sure that the man in the yellow suit is a good or trustworthy person. Her willingness to place her trust in him anyway shows how alone and unmoored she feels at this point and illustrates that she’s not yet ready to handle adult situations on her own. By introducing Winnie to the water cycle, Angus is able to introduce Winnie to the cycle of life using a metaphor that Winnie will be able to see and understand in real time.
Angus and Winnie drift in silence and watch the sunset. After a bit, Angus says that after the water reaches the ocean, it evaporates, moves back over the land in clouds, and falls into the streams as rain. He says that it's part of a wheel, along with the animals and people, and it's always supposed to grow and change. They reach the far side of the pond and the boat bumps into some weeds and branches. Winnie watches the water continue past this obstacle. Tuck repeats that the water will continue on but says that the Tucks are stuck, just like the boat. They're not part of the wheel anymore, though everything around them, including Winnie, is growing and changing.
Running the boat into the branches and likening it to the Tucks is a very obvious way for Angus to tell Winnie how he and his family are forced to live because of their immortality. His tone also makes it clear that he believes this isn't a good thing; the water, he suggests, is able to complete a correct and natural journey while the Tucks are like the man-made and unnatural boat and can only go certain places. This moment hints that part of the purpose of life is actually death.
Suddenly, Winnie understands what Angus is saying. She'll die one day, without a question. Feeling helpless, she says she doesn't want to die. Angus says calmly that she'll have to someday, as it's important and necessary to live the entire cycle of life. Angus says that as someone who can't die, his life is somewhat useless and he's barely living. Winnie is amazed, as nobody has spoken to her like this. Angus gruffly says he wants to grow and change, and he wants to die, but he didn't know he felt this way until after he drank the water. He says that if people knew about the spring, they'd all drink the water and nobody would know until after that it's a horrible fate. Winnie feels numb and watches the water. Miles interrupts her reverie and yells that someone stole the horse.
The very fact that Winnie is amazed to be spoken to like this indicates that she hasn't had experiences where adults in her life level with her and treat her like a fellow adult, as Angus does here. Winnie's reaction shows that engaging with a child like this has the potential to make that child understand very mature concepts, even as these concepts shock and numb Winnie. When Angus insists that he's useless because he can't die, he makes it explicit that in order to truly live, one must also die and complete the cycle.