Disclaimer: Needless to say, this version of the story of Tuor and Idril wouldn´t find a place in Tolkien´s views on his world (actually, this is more like Ovid...). But Tolkien´s own possible solution to the problem of their fate would equally go against his views if it were true. The characters are his.
"In those days Tuor felt old age creep upon him, and ever a longing for the deeps of the Sea grew stronger in his heart. Therefore he built a great ship, ande he named it Eärramé, which is Sea-Wing, and with Idril Celebrindal he set sail into the sunset and the West, and came no more into any tale or song. But in after days it was sung that Tuor alone of mortal Men was numbered among the Elder Race, and was joined with the Noldor, whom he loved; and his fate is sundered from the fate of Men." (The Silmarillion, Of Tuor and the Fall of Gondolin.)
The Land of Gift
"What do you see?"
The woman leaned on the railing, looking westward. Unlike those of the man who sat huddled on the floor to escape the bite of the chilly sea breeze, her eyes were bright and piercing, and bereaved of all hope.
"What do you see?" the hoarse voice repeated the question, after a while of uncertain silence. She lowered her glance, refusing to turn back to face him.
"Nothing."she whispered, as if afraid of her own words. Still, the answer reached the man´s hearing, and she saw him frown in pain.
"Maybe if we go further..."
"Do not comfort me!" he spat. Enlivened by a new fire, he struggled to his feet and started pacing in circles around the deck, refusing her hand when she tried to help him. "The way is closed, too well I can see it though my own eyes falter. They have forsaken us. We are lost!"
Idril looked at her husband, old and marred by the passing of Time. She saw the expression on his wrinkled face, and understood.
"It is time." he muttered, halting his pace to stare at the Sea that he had once loved so much. The light in his wife´s eyes dimmed in a brief cloud of agony.
His features softened, but he shook his head.
"You must understand. "he said. "Now, I still can stand on my feet and command my own movements. If I wait –if we wait, a day, a week, a month further, you will rise one morning to find me gone beyond the Circles of the World, and you will embrace nothing but my hideous carcass." His expression soured, and twisted into a grimace. "The Valar have forsaken their errand-boy, and you are not Lúthien the Fair!"
Idril´s eyes sought the same horizon where her husband´s glance was lost. She said nothing, showed nothing, but the lines on her face hardened and straightened until she looked like the ivory statue of her mother in the gardens of her Gondolin palace. Then, she stepped in front of him, barring him from the view of the Sea.
"It calls to me." he muttered. She nodded, slowly.
"Then, you will not go alone."
There was shock in his eyes, and as it passed, denial.
"You will not do such a thing." he hissed. "I will not allow you!"
The anger and refusal of this old man were too weak to even touch the fëa of an immortal. Idril´s heart brimmed with pity, even as she shook her head.
"No, Tuor, you will not prevent me. "she said. "I am not Lúthien the Fair, but I will fear nothing to stay with you forever, like the daughter of Thingol and her mortal husband."
"If I leave this ship, no walls will rise between you and the Undying Lands!" he sputtered, with increasing nervousness. She shook her head again.
"I am an Exile. They will have no more mercy on me than on you."
His expression was forlorn, frightened like that of a child who had found that his bright mother was not strong enough to protect him from the evil of his own kin. She repressed the memories of darkness and roaring fire, and fixed them on the beckoning waves of the Sea.
"You are so beautiful, Idril... untouched by mortality, unmarred. You-you cannot wish for a watery tomb, next to an old man..."
A wrinkled hand caressed the white perfection of her cheek. Once, she remembered, she had risen from her sleep to find the contrast heartwrenching, and then she had felt the long dormant echo of Fëanor´s words against the Valar fill her heart like an insidious poison.
Who were they trying to fool? A wry smile crossed her lips. She could never have hoped to tread the plains of Valinor again. She was marred beyond redemption, like all the Noldor who had heard the fiery words in Tirion that night. Elenwë had tried to cover the ears of her child, but she had heard them, and now there was nothing but ugliness beneath the veil of her beauty.
Her smile widened, firm and steely like the gleam of iron.
"I chose this long ago."
The Great Sea had become stormy, mirroring masses of black clouds on its turbulent surface. Violent waves crashed against the bow of the ship, as if Ossë knew what they were going to do and was fighting to reject them. Feeling a light feyness overcome her spirit, Idril looked at them, took Tuor´s hand in the grip of hers, and laughed in defiance.
No one could stop them now.
The old man climbed with great effort, but in his pride he refused to ask for help. She followed immediately after, her movements agile and balanced.
As they were both perched on the prow´s treacherous support, Tuor turned back again, to stare at the pale lines of her face. She smiled warmly at him, at his white hair mingling with her gold by the might of the wind, and for a moment she did not look like a ghost.
"I remember the first time I looked upon you, standing next to the throne." he whispered. "Back then, I thought that the Seven Gates of Gondolin had been built to protect you from the wind of the North. "His features contorted in pain. "Little did I know that it would push you to your fall."
Idril took his hand again, and this time she did not let it go.
"The first time I looked upon you, you seemed to me one of the Valar."she replied. "Little did I know that you would defy them in the end."
Tuor´s lips curved in a small, bitter grin. As he pressed her delicate hand, and with it the youth and beauty that had left nothing but a deep scar in his spirit, he turned his gaze towards the grey Sea.
"I will now perform the last of my great deeds. May the Valar grant the Secondborn the mercy that they did not grant me!"
Idril´s violet eyes glittered.
"May they stand up from their thrones and know of us." she said. But then, before she fell, she added in a whisper "And may our doom haunt them in times to come."
As their joined bodies pierced its surface, the waves froze and disappeared, the wind abated, and the Sea fell to an eerie calm.
And then, from the waters where Idril and Tuor had sunk, a great noise exploded.
First, it was a ragged peak of land, emerging from the deep in a commotion that reduced the empty ship to splinters. Then, the waters surrounding it began to rage, and five other peaks broke the surface and avidly sought for air, star-shaped, growing long and tall like proud arms of land.
Green and fair meadows stretched under the skies, wet and gleaming from the water whence they had come. Mountains, hills and mounds struggled up next, and high cliffs where streams of white foam fell back to the the Sea, and mingled with the golden gleam of the sun in a triumphant roar.
And even many years later, when the Men who inhabited the island walked its shores at dawn, it was rumoured that a man and a maiden could be sometimes seen holding hands and dancing among the breaking waves.