It is a large boat with a wooden exterior with windows and a door on it. There is also a banner on it that reads "Camp Sun-N-Fun or Bust!" in orange text.
Role in episode
The Sun-N-Fun boat is seen at the beginning of the episode, where a bunch of kids are boarding it, ready to go to Sun-N-Fun Island. SpongeBob intends to go there by getting on the boat as well. However, he and Patrick hug for too long, not knowing the boat left, and the boat to Inferno Island comes instead.