Pick out one or two lines from John Masefield's "Sea Fever" that contain alliteration. What is the effect?

The term "alliteration" comes from the Latin word "littera," which means "letter of the alphabet." In poetry, it is a stylistic device that uses the repetition of the same first consonant sound across the start of two or more words in a line of text.
The famous poem "Sea Fever" by John Masefield tells of the longing and wanderlust of the poem's narrator to return to the sea and sail away aboard a ship. Two of the most powerful uses of alliteration are in the first and third stanzas. In the first stanza, Masefield uses the repetition of the letter "s" in the first two lines to give a musical quality to the words, almost as if the narrator were singing the words instead of merely speaking them.

I must go down to the seas again, to the lonely seas and the sky,
And all I ask is a tall ship and a star to steer her by . . .

In the second line of the third stanza, Masefield repeats the letter "w" over and over, which evokes the sound and feel of the wind so clearly that readers can almost feel it themselves.

To the gull's way and the whale's way where the wind's like a whetted knife . . .

There are other examples of alliteration in the poem, such as the "c" sound in "the wild call and the clear call" and the "s" sound in "the flung spray and the blown spume, and the sea-gulls crying," but the above examples are the most evocative.