Disclaimer: Sherlock Holmes and John Watson belong to Sir Arthur Conan Doyle and all others who have purchased the rights to them. I'm just a little fanfic writer who looks up at the stars and wishes I could do that.

A/N: In my science class we had to write a story about a polluted river, explaining how it was polluted and how to fix it. Naturally, like the hopeless addict I am, I used the boys. And apparently I got 60/50, although I'm not sure if that was a typo on the grades or not. xD Enjoy.

"Dear me," sighed Sherlock Holmes. "This is quite a problem, isn't it."

"A problem indeed, Holmes," Doctor John Watson agreed, walking along beside his friend and looking down at the gooey, slow-moving river next to them. "How could it have happened?"

"Well I was just reading my case notes and I turned the page too fast."

Watson blinked. "What are you talking about?"

Holmes glanced at him. "This papercut. What are you talking about?"

"The river!"

He looked over. "Oh dear. That is a problem. How on earth could this have happened, Watson?"

"You're the detective, Holmes, you tell me."

"Excellent point." Holmes stopped, clasping his hands behind his back and scrutinizing the water. "Watson, I have reached a conclusion."

"What is that, Holmes?"

"This river is abominably disgusting."

"I must agree, Holmes. But what caused it?"

"Let us see if we can find out." The detective knelt down on the wet ground, gingerly poking his finger into the brownish goop.

"Ugh, Holmes, don't do that," Watson shuddered. "Who knows what diseases are floating around in there?"

"I suspect germs from cholera, a cold, the flu, dysentery, fever, hepatitis, and polio," Holmes said, flicking the thick water from his finger.

"And why do you suspect that?" Watson asked, absentmindedly poking the end of his cane into the water.

"Because it has been polluted by animal waste."

Watson immediately and rather frantically removed his cane from the river. "What gives you that idea?"

"That fish over there is dead, suffocated from an increase in bacterial population. The bacteria required more oxygen to survive, and the fish suffered. Besides, there is a large pig farm just up the river a little ways. Can't you smell it?"

"Unfortunately, yes," Watson muttered. "But surely one farm can't cause this much pollution."

"You're right, Watson. Some other force is at work here," Holmes said in a sinister tone. "Let us find out what it is." Rising from the riverbank, he set off at a brisk pace, leaving Watson hurrying to catch up.

"Aha!" the detective exclaimed, suddenly stopping. Watson bumped into him. "Goodness, doctor, trying to push me in?"

"No," Watson said, wrinkling his nose at the off-color water.

"I'm quite glad. This pollutant is even more dastardly than the first."

"Really? What is it?"

"Solid mineral substance, dissolved. Most likely carried here from the nearby mine by runoff from yesterday's rainstorm," Holmes explained.

"And what is it doing to the river?"

Holmes gestured to several floating dead fish. "Killing wildlife, and most likely harming aquatic vessels…not that I would attempt sailing in these waters."

"Especially since you have no boat," Watson said.

"Yes. That's a rather deciding factor. Shall we continue, Watson?"

The doctor sighed. "I suppose we should."

The pair resumed their walk along the river, until coming upon a section that was overflowing with green algae. They stopped again.

"This is a little better, isn't it, Holmes?" Watson wondered aloud.

"Far from it, Watson. This may be one of the most fiendish methods of pollution of all," Holmes said grimly.

"Well…isn't that just algae? That's natural, is it not?"

"Some algae is natural, yes. But this…this is an explosion of growth, and it is utterly destroying the ecosystem," Holmes replied.

"How so?" asked Watson.

"The algae grows at an unnaturally rapid rate, blocking out sunlight and killing some of the animals in the water. Then, after sucking every last nutrient from the ecosystem, the algae dies and bacteria begins to aid in its decomposition," Holmes said animatedly. "In turn, the bacterial population grows exponentially, and—"

"And uses up the oxygen," Watson finished.

"Precisely, Watson," Holmes said proudly.

"But what caused the algal bloom in the first place?"

Holmes knelt by the water's edge a second time and Watson knelt with him, looking curiously at the carpet of green. Once again dipping his finger in the water, Holmes promptly stuck it in his own mouth.

"Holmes!" Watson exclaimed, mortified.

"Hmm." Wetting his other finger, Holmes said, "You try, Watson," and quickly shoved it into his mouth. "What do you think?" he asked as Watson sputtered river water everywhere. "I agree. Fertilizer. Most dubious."

"Holmes…I feel it's about time to push you in the river," Watson growled, wiping off his mouth.

"I imagine it got there from agricultural runoff," Holmes speculated.

"I'm going home," Watson grumbled. "To rinse out my mouth many times with soap and water."

"But Watson, we must attempt to save the river!"

"And just how would we do that, Holmes?" Watson sighed.

"Elementary, my dear Watson. We must simply explain to the pig farmer that he must keep his sty cleaner, as well as requesting neater mining practices and less use of fertilizer," Holmes said.

"You really think that will work?" Watson asked.

"Perhaps," Holmes said. "Only time shall tell. Now, let us return home and wash out your mouth."

EDUCATIONAL VALUE! D: So yeah. Holmes is going green. Love it. And review. :)