Merchant Ship is a 0/2 that can’t attack unless your opponent controls an Island. Why would you attack with a card with 0 power at all, anyway? If you attack with it, and it isn’t blocked (little chance of that, really) you gain 2 life. Oh, wow, 2 life?
Also, if you control no Islands, you must sacrifice this card. This is a little odd, since if you’re playing this card nine times out of ten you will control an Island. In any case it’s pretty weak, especially for an uncommon from Arabian Nights!
Still, Merchant Ship is on the Reserved list. It’s probably worth having a copy just for collection’s sake. After all, decent condition copies of Merchant Ship can sell for as much as $5 or more on TCGPlayer. And while it’s a really mediocre card, the occasional Ramirez DiPietro or Skeleton Ship Commander deck will play a copy.