It is, of course, possible to scan the poem, but this particular poem does not appear to have a standard meter or rhyme scheme. Instead, it is written in free verse, which means that it lacks both of these. I will highlight the accented syllables with bold font below as well as label the end rhyme. Wherever you see the same letter in parentheses at the end of lines, that means that those lines rhyme: for example, lines marked with (c) rhyme with other lines that are marked with (c), and so forth.

Look, stranger, on this is land now (a)
The leaping light for your delight discovers, (~b)
Stand stable here (c)
And silent be, (d)
That through the channels of the ear (c)
May wander like a river (~b)
The swaying sound of the sea. (d)

Here at a small field's ending pause (e)
Where the chalk wall falls to the foam and its tall ledges (f)
Oppose the pluck (g)
And knock of the tide, (h)
And the shingle scrambles after the suck- (g)
-ing surf, and a gull lodges (f)
A moment on its sheer side. (h)

Far off like floating seeds the ships (i)
Diverge on urgent voluntary errands, (j)
And this full view (k)
In deed may enter (~l)
And move in memory as now these clouds do, (k)
That pass the harbour mirror (~l)
And all the summer through the water saunter. (~l)

There is assonance, the repetition of a vowel sound (in this case "ah"), in stanza two with the words small, pause, chalk, wall, falls, tall, knock, and lodges. The same sound recurs in the third stanza with the words far, off, on, and voluntary. There is alliteration, the repetition of the initial consonant sound, in several places. In stanza one, there is repetition of the opening "L" sound in look, land, leaping, and light. There is also repetition of the initial "s" sound in stand, stable, swaying, silent, and sea. In stanza three, there is alliteration of the "f" sound in far and floating, and then again with the "s" sound in seeds and ships; in fact, seeds and ships also create consonance, the repetition of the final consonant sound "s". There are a great many other sound devices used throughout the poem as well. Therefore, though it may not have regular rhythm or rhyme, the poem itself is still very reliant on the music it produces.

Scanning a poem can sometimes yield results that are a little messy or ambiguous. The meter here is mostly iambic, that much is clear, but the number of stresses per line in each stanza varies quite a bit. I can find five stresses in the first line of each stanza if I look for them, but I often hear differing number of stresses in the other long lines. The short lines, at least, often or always have just two stresses.

The rhyme scheme seems prettty easy to determine by comparison, but it's nothing that seems familiar to me:

X X A B A X B

"X" here signifies any sound that doesn't have a rhyming partner.

Alliteration (and, more precisely, sibilance) is problem the most obvious and consistently used sound device in this poem.

How do these elements contribute to the poem's meaning? Maybe the varying line lengths, occasional rhyme, and alliteration help reinforce the notion of the rhythmic motions of the water, the "swaying sound of the sea."