Teru tsuki no nagaruru mireba ama no gawa izuru minato wa umi ni zarikeru - Tosa Nikki(English Translation & Meaning)

てる月のながるゝ見ればあまの川
いづるみなとは海にざりける

Roma-ji: Teru tsuki no nagaruru mireba ama no gawa izuru minato wa umi ni zarikeru
English Translation: Watching the bright moon
flowing down across the sky,
the harbor-mouth where
the River of Heaven flows
out is in the sea, it seems
Meaning: Watching the shining moon drift down and sink into the waves, I realize that the mouth of the River of Heaven opens onto the sea.
Commentary: 17 The Eighth Day of the First Month: The Moon Setting into the Sea

On the eighth day of the first month, something prevented their departure, and the party remained at Ōminato. That night the moon sank into the sea. Seeing this, the diarist recalls Ariwara no Narihira's line "yama no ha nigete irezu mo aranamu" and wonders whether, had Narihira composed it by the sea, he would have said "nami tachisaete irezu mo aranamu" instead.
Ariwara no Narihira was a poet of the early Heian period and one of the Six Poetic Immortals. The poem recalled here, found in the Kokin Wakashū and The Tales of Ise, is "Akanaku ni madaki mo tsuki no kakururu ka yama no ha nigete irezu mo aranamu," composed on a night of hunting to keep Prince Koretaka from retiring early to his chamber.
This poem was composed by a certain person who, recalling Narihira's poem, watched the moon sink into the sea.
The diary records no response to this poem. Poems of the moon continue later, with "Minasoko no tsuki no ue yori kogu fune no sao ni sawaru wa katsura narurashi" on the seventeenth day of the first month and Abe no Nakamaro's poem on the twentieth.

The first line, "Teru tsuki no," means "the shining moon." The second line, "nagaruru mireba," means "when I see it flow," as the moon glides across the sky and sinks into the sea; "nagaruru" (flowing) is a word associated with the "ama no gawa" (River of Heaven) that follows. The third line names the River of Heaven, imagining the moon carried along on its current.
In the fourth line, "minato" means a water gate, that is, the mouth of a river. In the final line, "umi ni zarikeru," "zari" is a contraction of "zo ari," closing with the wonder of discovery: so it was in the sea.
Where Narihira's "Akanaku ni madaki mo tsuki no kakururu ka yama no ha nigete irezu mo aranamu" lamented the moon slipping behind the mountain's rim, this poem transposes the scene to the shore, where the moon sinks into the sea, and playfully reasons that the River of Heaven must empty into the ocean.
Author: Ki no Tsurayuki
Source: Tosa Nikki
Prev Poem: Yuku hito mo tomaru mo sode no namidagawa migiwa nomi koso nuremasarikere
Next Poem: Omoiyaru kokoro wa umi o wataredomo fumi shi nakereba shirazu ya aruramu