To a certain extent, one can see the speaker in H. D.'s short poem “The Pool” as unwittingly imposing her lack of stable identity onto the natural world around her. In other words, the speaker doesn't know what the creature in the pool is because she doesn't know herself; the natural world is a mystery because she's a mystery to herself.
On this reading, the opening line “Are you alive?” could be said to apply to the speaker as much as to the strange, unknown creature in the pool that quivers “like a sea-fish.” By the same token, the very last line of the poem—“What are you—banded one?”—could also be interpreted along similar lines.
Perhaps the speaker's face appears “banded” by her net as she looks at her reflection in the pool. This would appear to add plausibility to the theory that the quivering creature in the pool is in fact a projection of the speaker's mind. In seeing her reflection in the water, the speaker is seeing herself, not just her outer features but also her inner self. And given her lack of stable identity, what she sees is strange and mysterious. This would explain why she is so puzzled by what she sees.