From source to mouth there's but one ford --
And that cannot be crossed --
Where Ferdiad was gripped and gored;
His best friend won and lost
      The water's red from brink to brink,
      The Morrigan comes down to drink;
      And the river goes on south.

Right close in shore, to ward off cold,
      An angler sucks a jug.
The water seals and gets its hold;
The angler feels and gives a tug.
      Above the ice he's having fits,
      Below the ice a long tail flits;
      For the river takes it south.

Steeped in the vacuum of her dreams,
A mirror's empty till
A man rides through it. Once she gleams
And once she moves, then she is still.
      The filament snaps in the light,
      But yet she is a lovely sight,
      As the river bears her south.

The gold a dragon could not keep
Came to a woman's hand;
Then thieving kinsmen, diving deep,
Found out a safe in sinking sand.
      Dying, they would not tell the place,
      Nor does the water yield a trace,
      As the river sweeps on south.

---

Ferdiad was Cuchulainn's friend and foster-brother; Cuchulainn killed him in single combat at a ford of the river Dee. The Cattle Raid of Cooley, Irish saga of the Ulster Cycle.

The Morrigan was a Celtic battle goddess. Statue of the Morrigan (commercial site); (copy on non-commercial site) Big, beautiful, expensive book at Amazon.com: The Great Queens : Irish Goddesses from the Morrigan to Cathleen Ni Houlihan (Irish Literary Studies, No 34)

The angler is an allusion to Piscator himself. The Complete Angler at Amazon.com or online.

The third verse alludes to The Lady of Shallot by Alfred, Lord Tennyson. The Lady of Shallot was told that she must weave a "magic web" and never look out of the window toward Camelot; if she did, she was doomed. She watched the outside world in a mirror while she wove. One day Sir Lancelot rode by, singing. She went to the window and looked out. The mirror broke, and she pined away for love of the singing knight. She had her body lain in a boat and cast adrift toward Camelot. A painting of the Lady by John Waterhouse

The location of the historical Camelot is hotly contested. In Tennyson's day majority opinion favored Winchester; therefore in this verse the river would be the Itchen.

The fourth verse refers to events in Wagner's opera cycle The Ring of the Niebelungs; Wagner got the story from the Old German epic poem the Nibelungenlied; which came from the Old Norse Volsunga Saga.

The dragon Fafnir was slain by Sigurd; Sigurd's widow Gudrun received the gold as dower. Her kinsmen Gunnar and Hogni hid the gold in the river Rhine.