Shrek trudged through the swamp, his large, green feet squelching in the mud. He waved a hand in front of his nose, grimacing at the sulfurous odor that seemed to cling to the air around him. "Blimey, what died in here?" he muttered to himself, glancing around for the source of the smell.

Scooby-Doo poked his head out of the van, his nose twitching as he sniffed the air. Shaggy, standing beside him, looked equally puzzled. "Like, Scoob, do you smell that?" he asked, his voice a mix of curiosity and apprehension. "Ruh-roh, Raggy," replied Scooby, his eyes widening as he caught sight of Shrek approaching.

Shrek stopped short, raising an eyebrow at the group of teenagers and their talking dog. Velma adjusted her glasses, peering up at the towering ogre. "Jinkies! An ogre in the swamp! That explains the smell," she exclaimed, her voice filled with excitement at the prospect of another mystery.

Fred took charge, his voice confident and authoritative. "Alright, gang, it looks like we have another mystery on our hands. Shrek, do you mind helping us out?" he asked, turning to the ogre. Shrek shrugged, a reluctant smile tugging at his lips. "Why not? I could use some company," he replied, his voice gruff but good-natured.

Daphne pointed ahead, her voice tinged with excitement. "Look, I think I see something!" she called out, her flashlight illuminating a strange, bubbling pool. The group gathered around, watching as the surface of the water churned and hissed, releasing puffs of sulfurous gas into the air.

Velma knelt beside the pool, examining the strange formation. "It's a natural sulfur spring!" she announced, her voice filled with triumph. Shaggy and Scooby sighed in relief, their expressions relaxing. Shrek chuckled, shaking his head. "Well, that explains a lot," he said, his laughter echoing through the swamp.