I really like your Elros and Elrond. It is a lovely story with a perfect pace and sense of internal integrity. I have very different personal canon of a lot of it, but I completely suspended my disbelief while reading. I really enjoyed it.

Mewlips indeed! Everytime I see that word it makes me laugh. You tapped into that here.

The central conceit--Elrond and Elros trying to learn to sail--is both an uncommon one and one that has an obvious logic when you come to think of it. (I can remember occasional references to Elros learning to sail, but can't recall anything that involved Elrond, just at the moment.)

What you spin out of that idea works extremely well, too: the themes and your characterization of the two brothers, dealing with the past, in their different ways, and foreshadowing future decisions.

Welcome to the First Age!