Before looking at the first stanza of the poem, it's worth considering the specific word choice for the title. The poem is about a specific animal commonly known as the blue whale, but the title uses the very scientific-sounding "Cetacean." This word refers to the biological order Cetacea, a large group of aquatic mammals (totaling 89 species of whales, dolphins, and porpoises), and signals one of its main themes: the quest for knowledge and understanding. The scientific title speaks to the practices of observation, assessment, and classification—more broadly, to humanity's insistence on categorizing the natural world.
The poem then starts by describing the speaker's boat trip to "observe Blue Whales." The speaker and others have woken up early on a Sunday morning and sailed off the San Francisco coast in a boat "sixty-three" feet in length. The precise measurement here reflects the speaker attempts to chronicle the experience of seeing the whales in precise language.
Also note how the poem starts with a bunch of short phrases lacking any conjunctions. This asyndeton creates a choppy, detached tone. The poem thus seems remarkably spare and unsentimental so far—almost like a scientist's brief field notes.
But, already, there's more going on here than meets the eye. First, note that it's a Sunday—which in Christian tradition is the day of rest. Perhaps, then, it's not too much of a stretch to think of the poem's set-up as a subtle nod to a kind of human restlessness when it comes to making sense of the world.
It's also worth noting how the poem makes no effort to build a will-they-or-won't-they-see-the-whales kind of suspense. After the caesura in line 3 (that dash after "Whales"), the speaker makes clear that the group did in fact spot some of the creatures "off the Farallones" (a group of islands in the Pacific Ocean). The poem thus immediately becomes about the encounter itself, and not whether that encounter is going to happen.