The speaker begins reluctant. She doesn't like adventure, and her mind runs to alligators, deep water, and some vicious presence waiting far from home. The long train ride, with whistles echoing in her sleep, pulls her away from everything familiar.
Then the poem shifts to Ten Thousand Islands, and the fear gives way to close, patient looking. Shells are everywhere: in the shallows, dripping from mangrove roots, grinding under the canoe. The speaker notices sand crabs, strange fish, mosses, bromeliads, and mosquitoes. The Calusa are named as the people who shaped this land alongside the mangroves, which gives the place a deep human past.
The mood turns from anxious to hushed and almost meditative. Repeated words like "drip," "shell," and "grinding" create a slow rhythm, like rowing. The tide that made going out easy also carries her gently back, and the poem ends with the water's calm gray-green. Judging by the contrast, the place has quietly won her over.