Who is liable for transactions in onboard shops on cruise ships?

In 2007 I bought a Seiko watch in an onboard shop on the Royal Caribbean's Navigator of the seas. It was marketed and sold to me as a ceramic watch.
I recently took it to a jeweller for a new battery and he advised that it needed a repair and told of the cost to sent it to Seiko. I mentioned that it would be worth the cost as it is a ceramic watch. He looked closely at it for a few minutes and announced that it was not ceramic but was ion-plated.
I contacted Royal Caribbean and they told me that their onboard shops are operated by Starboard Cruise Services and I should take up this mis-selling with them as they (RC) are not liable. At the moment I am still in communication with Starboard Cruise Services and await their response.
This led me to think about who is ultimately liable. One answer may be, as I understand it, the analogy with the high street. I if I had an issue with a transaction in, say, Clarks shoe shop I would take it up with Clarks, and not the property company from whom they rent the premises.
However, there is a crucial difference on a cruise ship. If you bought a pair of shoes from Clarks you would get a Clarks receipt and the shop is clearly badged as 'Clarks", so there is no doubt with whom you are dealing. On a cruise ship, the shops are promoted by the cruise company, there is nothing (expect maybe in miniscule small print somewhere) to say that the shops are operated by a third party, the transaction is effected through your cruise account and, in my case, the receipt is a Royal Caribbean receipt.
Finally, an added complication is that due to tax reasons, the shops are only open when the ship is in international waters.
I realise it was 12 years ago and any relevant legislation may no longer apply but, for the sake of future purchases, does anyone have knowledge of what law applies and who is liable?