How wonderful, in me the shoreless ocean, the waves of individual beings arise, play, and disappear according to their own nature
This shifts the same claim from the impersonal cosmos to individual beings specifically, the harder case, since particular people, not abstractions, ordinarily provoke attachment.
Where the previous verse pictured the universe as a single ship, this one turns to the plural, individual beings, each treated as its own wave rising, playing, and disappearing according to its own nature within the same shoreless ocean. This is, in a sense, the more demanding version of the same claim: it is one thing to say the cosmos as a whole does not disturb the self, and another to say that no particular person's arising, behavior, or departure disturbs it either, since it is specific beings, not an abstract universe, that ordinarily provoke attachment or grief. "According to their own nature" repeats the causal move from the ship verse, crediting each being's conduct to its own svabhava rather than requiring the ocean-self to manage or take responsibility for it. The three astonished verses of chapter 4 together move from the general, the universe, to the specific, the ship, to the personal, individual beings, closing the chapter on its hardest and most intimate application.
How wonderful! In me, the shoreless ocean, the individual being arises, plays for a while like a wave, and disappears, according to its own nature.
Ashtavakra Gita