Fizzles' Folly is a boat owned by hunter Garth Fitzgerald IV.
The boat is docked in Warsaw, Missouri and was used as a demon-proof safe house for prophet Kevin Tran, while he attempted to decipher the demon tablet for the Hell Trials. Dean chose not to ward the boat against angels for the sake of Castiel finding this place.
However, Crowley was able to break through the warding and abduct Kevin. The boat has not been seen since. The Men of Letters bunker is about a six hour drive away from the boat.