In case anyone is interested the puzzler answer is completely bogus. Of course I discovered this using the internet to cheatingly come up with the answer:
good old snopes
I believe the reference to “not tanning” is misapplied here. Nineteenth century and earlier ships had no air conditioning and being on the COOLEST side of the ship (Port Out and Starboard Home) made for the most comfortable travel. Victorian English folks stayed fully dressed , even in the tropics, and wore large hats to keep the sun away from their faces, and it did not really matter which side of the ship they were on from a tanning point of view.
Similarly, the expensive tickets to a bullfight in Spain are “Sombra” tickets, those in the shadow side of the bull ring.
Well, that Snopes article is quite interesting and informative. Thanks! I’d heard the “port outbound, starboard home” story before, so just figured it was correct.