I too had been struck from the float forever held in solution, I too had received identity by my body, That I was, I knew was of my body—and what I should be, I knew I should be of my body.
He compares the boat on the water to a scientific specific that is preserved "in solution" to keep it fresh. It feels like time is frozen.
Then there's another characteristic Whitman moment: he expresses comfort and acceptance of his body. One of Whitman's big poetic goals was to root out the shame and squeamishness about the body. Unlike many philosophers, he does not agree with the sharp distinction between body and soul.