Look in any nautical antiques list and in the top five you’ll see a porthole. This link offers one story of their origin. I think portholes are best experienced from inside the vessel. Judge for yourself: wouldn’t you love to wake up to this light experience?
Views beyond the porthole can be quite magical as well.
I learned recently why port holes are open only in port: I was below decks in a stiff wind that had the schooner heeled over. Holding the companionway ladder, I happened to glance at the porthole: beyond the glass was water, water up over the starboard caprail and alongside the cabin house.
Wonder what they saw through the portholes of this vessel in Belgium.
As magical as they can be, porthole diameter turned tragic in the great waterfront fire of Hoboken, June 1900. Passengers aboard the Saale were unable to escape because the portholes were too small to allow egress. Here’s a much longer article with photos on the fire that engulfed several North German Lloyd vessels.
To return to lighter fare, check this out, “Destiny,” one of my favorite paintings by John William Waterhouse.