A reference to Alfred Tennyson's poem Morte D'Arthur:
Morte D'Arthur, last verse: So said [Arthur], and the barge with oar and sail Moved from the brink, like some full-breasted swan That, fluting a wild carol ere her death, Ruffles her pure cold plume, and takes the flood With swarthy webs. Long stood Sir Bedivere Revolving many memories, till the hull Looked one black dot against the verge of dawn, And on the mere the wailing died away.