I don't know if there are written descriptions of Elven ships, aside from those of Galadriel and Celeborn, but I have one of Tolkien's own paintings which shows one in the book
J. R. R. Tolkien: Artist and Illustrator. The watercolour is called
Halls of Manwë (Taniquetil) and in the foreground a swan-shaped ship with one sail and four sets of oars can be seen. I shall attempt to find a copy of the painting online and edit this post to include the link if I do.
Link:
Book with painting
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'Mercy!' cried Gandalf. 'If the giving of information is to be the cure of your inquisitiveness, I shall spend all the rest of my days in answering you. What more do you want to know?' 'The whole history of Middle-earth..
.'