flying dutchman

I don't think Flying Dutchman could be a character in this movie, but then again he could serve as like a character for knowledge on what this creature is.

ok

his boat is a ghost boat

Well, since the s!udge has thus far been restricted to mostly bikini bottom, I wojldnt be surprised if it started to venture further out, like to mrs. Puff's place, jellyfish fields, or even further out, like to places seen in unusual episodes, like the deep sea.

I actually did write a scene with Mrs. Puff in the movie, where "SpongeBob" shows up at the boating school as it's raining, but when she tries to ask him why he's there he doesn't answer, when she tries to shut the door on him he wedges his foot in the door, she threatens to call the police on him before he takes off his scarf and reveals there's nothing below his eyes. Then he begins to form into his Sludge form with the black eyes and greyscale appearance, his eyes widen and chase Mrs. Puff around the classroom before swallowing her whole with his eyes, carrying her out of the school and up towards the sky, the lightning strikes and reveals the "cloud" as the rain is falling upward towards it.

Oh damn, that's good storytelling already!
Ngl, I got a slight chill from that!

Or another scene where SpongeBob is coming home from work one night, but takes a cut from Jellyfish Fields as a shortcut, but on his way home he encounters a singular cloud raining in the middle of the field, this is odd because he remembers Perch Perkins on the news mentioning a cloud that hasn't stopped raining for six hours, he walks over to investigate the area but finds out some oddities, he notices the area where it was raining made little to no sound, not even the rain hitting the ground, and it formed no puddle, but what happened next gave SpongeBob chills, the rain came to a halt, it didn't stop with one drop at a time it just stopped, like a car braking. Then SpongeBob felt rumblings coming from below his feet, then he heard the cloud make the strangest noise he ever heard, kind of like the sound of a whale, what happened next was absolutely bone chilling. The rain began coming from the ground, falling upward towards the cloud, SpongeBob began to hear ringing in his head, making him dizzy, but then the rain-like substance began to wrap around his feet and ankles. SpongeBob now horrified ran away as fast as he could from the cloud, immediately hiding inside his house.