Bad Luck Day is a SpongeBob Squarepants book.
In the book, Patrick picks up a Kings crown seashell. Though Patrick picks it up innocently though SpongeBob had warned him that it was bad luck. The next day, Patrick realizes that it is bad luck saying, "I'm having a bad luck day." Though SpongeBob tells him that, that shell is nothing but a normal shell. But Patrick keeps having bad luck, so SpongeBob and Patrick remove every shell from there houses. And with the bad luck Patrick makes sure he isn't stepping with his left foot first. But the bad luck keeps happening and they incounter the Black Snail. Though SpongeBob and Patrick find a way to end Patrick's bad luck, and the story ends.
- In this book Patrick says that his mom can't swim.
- The Black Snail makes an appearance in this book.