The prompt for this one was for the Antagonist Lewis AU, where Lewis is a stereotypical Scooby-Doo villain after Arthur's head before he eventually rejoins the group. Basically Arthur is trapped in a sea cave with high tide coming in fast. Does Lewis save him?

Arthur was beginning to think he had a curse put on him at a young age. He tried not to think about how many times he almost died in the last half hour.

As if going into another cave wasn't bad enough, but then the damn thing had to collapse all around him, Vivi, and Mystery. He had pushed Vivi to safety but in the process had fallen into one of the many cracks in the ground created by the sudden cave in.

He wasn't sure if it was luck or otherwise that landed him in the ocean below. On one hand the water did soften his fall. On the other…

"AUGH-!"

The circuits on his arm began to short out and Arthur swore his whole body went numb; the shortage gone straight to his nerves. He felt himself sink in the water and began to panic. If being electrocuted didn't kill him then he would certainly drown.

The arm had to go! He barely had enough time to register this before the feeling returned in his other arm and he quickly removed his prosthetic. Arthur didn't pay it any mind as it began to sink to the depths below. He only focused on getting air.

Swimming with one arm was a lot harder than it looked. It didn't help that he naturally sucked at swimming anyway.

But finally he managed to break the surface and gasp for air, rapidly kicking until he found some solid ground. For a while he just held on with his remaining arm, trying to catch his breath, until finally he found the will to pull himself up onto the rocks. Slippery or not, somehow he found a way.

And then he sat and waited, clutching his stump of an arm left. Waited for what? Even Arthur wasn't sure. There was no way Vivi would find him down here. He was on his own.

After a few minutes of calming down, Arthur stood up on shaky legs and looked around. There had to be an exit here somewhere. He took one step and almost slipped and fell on his face. Right. Slippery rocks.

Alright, take two, and he made sure to be careful this time. He tried the wall, thinking maybe he could climb up somewhere to safety. Unfortunately that proved to be pointless. It was bad enough he only had one arm, but the rocks were so slippery that climbing was impossible. Arthur found that out the hard way after one attempt, sliding down the rocks and scraping his remaining arm rather badly.

He couldn't swim either. No way in hell was he getting back in the water. And there was no exit in sight. He was wet and cold and no amount of shivering would warm him up.

It felt like hours of searching before a feeling of dread suddenly overtook the mechanic. He was trapped…

So that's it? This is how I die? Being trapped in a goddamn cave? Somehow Arthur felt it was oddly appropriate. Poetic justice. He slumped in defeat against the rocky wall, clutching his stump of an arm like a lifeline. I wonder what'll kill me first…pneumonia or starvation.

Shame filled him as he felt tears start to prick at the side of his eyes. He didn't deserve tears but he couldn't stop them. He didn't want to die…not like this. There was still something he had to do.

"Lewis… I'm sorry…"

He hadn't expected it to feel this way. The cave-in hadn't exactly gone as planned but somehow it ended up better than what he had been anticipating. Vivi was safe and Arthur was left to rot down in the sea caverns below. He'd die slowly, painfully, and alone. Just like him.

So…why did this feel wrong?

Lewis wracked his brain for an answer. He should be happy. This was Arthur, his murderer. He was going to die in these caves and the ghost had a front row seat to it all. It didn't matter how long it would take; he was a ghost and had an endless amount of time to wait for the traitor's inevitable end.

He'd have his revenge.

He'd…

The ghost slammed his bony fist against the side of the cave. This wasn't right! He should be ecstatic about this but he wasn't! Instead it was almost he felt…sympathy for Arthur. Old feelings were starting to resurface. Their old friendship…how he had always comforted the blonde when he was terrified like this.

But those memories meant nothing to Arthur, so why should they mean anything to him?

"Lewis… I'm sorry…"

Said skeleton perked his head up at the sound. Did he just imagine that? The voice was so muffled that he almost brushed it off as nothing, but… He looked over to Arthur, who was curled up in a pathetic ball and quietly sobbing to himself. Lewis had made sure he was invisible the entire time of watching his former friend, but looking at him now…

"I'm so sorry…"

Now that he hadn't imagined. Arthur couldn't know he was there, right? No…no of course not. That was foolish. Arthur was no medium. If Lewis didn't want to be seen then he wouldn't be.

But then that begged the question: why was he apologizing to thin air? There was nothing to gain if he didn't know Lewis was there, watching, waiting.

…Lewis decided not to think about it.

As the time went by, Arthur hadn't moved from his spot. Every now and then Lewis would be able to hear a whimpered apology from his former friend and it only made his heart grow somber. No matter how hard he tried to convince himself, this wasn't right…

"Wh-?! Oh shit!"

Lewis was broken out of his thoughts at the first clear thing Arthur had said in hours. He was panicking and backing up against the wall. Huh, that was weird. Lewis didn't see anything remotely scary around him and the only thing by his feet were just rocks and the rapidly rising wa-

Oh.

Oh.

That's right, they were in a sea cave, weren't they? With the way the water was rising, high tide was coming in fast. This entire cave would be filled with water in a matter of hours.

So that's how it would go. Drowning. Not exactly the most picturesque death Lewis had in mind for Arthur but it would have to do.

Higher, higher. At first Lewis was thrilled to watch his former friend squirm and desperately try to find a way out with renewed vigor. It all proved pointless and soon enough the water was up to Arthur's neck. Lewis knew for a fact Arthur didn't float. He sunk. "Oh g-god… Help, someone please…!"

And that's when the feeling came back. How wrong the entire situation felt, it all came back full force and Lewis was almost overwhelmed. He watched as the water rose about Arthur's head and the stream of bubbles that followed. Arthur never did figure out how to properly hold his breath underwater…

Lewis was practically at war with himself. He couldn't still care for him. He didn't! He wasn't feeling sympathy for his killer at all!

Then the bubbles suddenly stopped and Lewis didn't think anymore. He lunged at Arthur's body, disappearing inside. While unconscious Arthur was even easier to possess. Lewis again tried not to think about it as he opened his newly acquired eyes. Instead of their usual amber, they were eerie magenta.

He quickly closed them again as they began to sting. Ow. Right. Salt water was a thing. Lewis forced Arthur's body upwards to the rapidly decreasing air pocket.

He'd almost forgotten what it was like to breathe. Arthur's body gasped for air and began to tread water as well as a one-armed person could. Unlike Arthur, Lewis actually could swim. Once that unfamiliar heart beat slowed down, Lewis took a deep breath (relishing in the feeling of air filling his lungs) and dove back under the water. He knew exactly where the exit was and prayed he could get there fast enough.

Somehow he made it.

Despite only having one arm, Lewis managed to get Arthur's body to the surface and drop it onto the shoreline. He stared at the unconscious body afterwards.

Why? He had the perfect opportunity to see Arthur die, and yet he…

"ARTHUR!"

Vivi's voice only made Lewis turn invisible. He had expected her to show up any second. Somehow she always knew. As he watched her try to shake the traitor awake, his thoughts came back to him.

'You want to be the one responsible for his death. With your own two hands. Where's the satisfaction in letting him die any other way?'

Yes. That had to be it. Somehow Lewis felt better at those words reassured him for his true purpose. His revenge would be complete.

But not today. He'd let him go for now.