Sharks
The best advice I can give anyone about buying art at sea is don't; I guarantee you will be ripped off. We amateurs are like lambs ready to be led to the slaughter as these sharks who call themselves art directors push their free drinks and spin the most outrageous lies.
To add insult to injury they also cream you for extra money by charging for inflated and worthless valuations..
There are no shortage of sellers on Ebay who are disappointed by the low bids they are receiving for their art after overpaying at these art auctions at sea.
It is especially risky to buy originals as these works are usually sold for thousands of dollars above their true value and it must be a sickening feeling for the buyer to discover their true worth when he decides to sell.
The valuations supplied by these companies are usually outrageously inflated; in some cases by over 500%. That is why they can sell you these so called masterpieces for "half price" and still make a fortune for the cruise lines and themselves.
A very popular story that they use to enhance Zamy's talent is their spin that Zamy was Marc Chagall's best student. If you still need more persuasion to buy, they will shed crocodile tears about his early demise, while telling  you  about the scarcity and inevitable rise in prices for his works.
I am sure that Zamy's art is becoming scarce and his prices are rising but if you overpay for any commodity, it is going to take a long time to recoup your losses..
At the prices you pay on board, it is unlikely you will recoup your money in your lifetime.
By all means go and attend these auction as invariable you will increase your knowledge about art but just don't buy as you will overpay for that piece of art.
Ebay is probably the best source for cheap art however the problem is you can't inspect the art up close and you may have to wait a considerable time until that special piece comes up for auction.
Most sellers are honest and transactions are mostly transparent although there are abusers.
One problem is Ebay sellers doing private listings.There is no excuse or reason to list privately unless the seller is bidding against the buyer. So if you like a piece and the seller is using private listings, email the seller and tell them that you want to buy but are not comfortable or prepared to accept these sort of buying conditions.
If you don't discourage this sort of behaviour, it will just spread.

Snipers.
I have expressed my opinion  about snipers in another guide, but I just can't help myself because I need to rail against them at every opportunity.
These annoying pests just don't know how to play fair and that is one of the most annoying thing about shopping on Ebay; these sneaks have an unfair advantage of surprise.
Even though you have done everything by the book, you can still be ambushed by some  social misfit with no conscience or ethics.
Nowadays if I really want a piece, I just assume that there is a sniper in the background and I make sure that I placed my highest possible final bid in the last minute.