A version of this story,The Children of Lir, which was regarded as one of the Three Sorrows of Irish Storytelling, can be found here: http://www.luminarium.org/mythology/ireland/childrenoflir.htm

Thomas Moore wrote a famous song to mark Fionnuala's role in the story

The Song of Fionnuala*

Silent, oh Moyle, be the roar of thy water,
Break not, ye breezes, your chain of repose,
While, murmuring mournfully, Lir's lonely daughter
Tells to the night-star her tale of woes.
When shall the swan, her death-note singing,
Sleep, with wings in darkness furl'd?
When will heav'n, its sweet bell ringing,
Call my spirit from this stormy world?

Sadly, oh Moyle, to thy winter-wave weeping,
Fate bids me languish long ages away;
Yet still in her darkness doth Erin lie sleeping,
Still doth the pure light its dawning delay.
When will that day-star, mildly springing,
Warm our isle with peace and love?
When will heav'n, its sweet bell ringing,
Call my spirit to the fields above?


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*To make this story intelligible in a song would require a much greater number of verses than any one is authorised to inflict upon an audience at once; the reader must therefore be content to learn, in a note, that Fionnuala, the daughter of Lir, was, by some supernatural power, transformed into a swan and condemned to wander, for many hundred years, over certain lakes and rivers in Ireland, till the coming of Christianity, when the first sound of the mass-bell was to be the signal of her release. — I found this fanciful fiction among some manuscript translations from the Irish, which were begun under the direction of that enlightened friend of Ireland, the Countess of Moira. [Thomas Moore's note to the song.]