Whirl up, sea— whirl your pointed pines, splash your great pines (1-3)
This is one bossy Oread speaking to the sea. She's commanding it forcefully, and she sounds darn sure that the sea will bend to her will. And she's already describing the sea in terms of the forest (especially when she uses the word "pines"). It's like she unites two parts of nature—the land and the sea—together with just her own poetic skill.
on our rocks, hurl your green over us, cover us with your pools of fir. (3-6)
Notice all those words for "us" in these lines? "Our rocks," "over us," "cover us." And all those repetitions of the word "your"? In these lines, the Oread draws a distinction between herself and her fellow land creatures, and nature, as embodied by the sea. If the Oread weren't trying too hard to bring everyone together, we might even think that there were a nymph vs. ocean battle going on. (Or, nymph vs. nature.)