This room was a temporary room. It could only be found in Club Penguin for a certain period of time during a party, event, or other. It may or may not have returned later.
"Yo ho ho! We MADE it! Welcome to the mysterious Shipwreck Island. Our journey is almost finished... just build the beacon and we're done! I wonder what's in that cave over there..."
It is believed that many ships got wrecked in this island, thus making the name Ship Wreck.
After you make the Lighthouse here, if you go back to Club Penguin Island and if you go to the Beacon and see from the telescope, you can see a red light glowing in the corner. That red light is the island's beacon, suggesting that all islands are near Club Penguin.