Do you have a reference for this?
Not to say its false, I'm just interested about the navies in Tamriel.
The chronicler can scarcely find a year throughout the First or Second Eras when the Maormer did not ravage the coastlines of the Altmer. As terrible as it was, it did force the Altmer to build a great navy to defend itself, and to this day, it is on the seas that the High Elves excel in combat. There are villages in the central valleys of Summerset that have never seen battle, but so much blood has been spilled along the coasts, it is a wonder it is not stained permanently crimson. - Summerset section of the Third Edition of the Pocket Guide
Indeed, the Colovians have taken to calling their enemy the "Old Mary" Dominion, for the womanly offensives of its Elven soldiers. The situation at sea, however, is another story, and the Dominion terrorizes the southern waters from the Cape of the Blue Divide to the Topal Bay. - Aldmeri Dominion section of the First Edition of the Pocket Guide.
It doesn't outright say they are the best, but their navy was notably more powerful than the navy of the Septim Empire. The Mede Empire doesn't stand a chance.
And there is MK's description of what the Altmer navy consists of:
Description of an Altmer ship:Made of crystal and solidified sunlight, with wings though they do not fly, and prows that elongate into swirling Sun-Birds, and gem-encrusted mini-trebuchets fit for sailing which fire pure aetheric fire, and banners, banners, banners, listing their ancestors all the way back to the Dawn.
This is Old Mary at Water.