Based on a piece of fanart I found. Kudos if you know the one.
John put down his book. It was quiet; too quiet. At least by 221b standards; it wasn't quiet unless there was some form of background noise like Sherlock roasting something over a bunsen burner.
The lack of this shouldn't have surprised him. He'd made Sherlock go take a bath after he and Sherlock had returned from a case and Sherlock had smelled like he hadn't bathed in days. If it hadn't been for John insisting he go take a bath, he doubted Sherlock would have of his own accord until the case was closed, which was looking a long ways off.
As John listened, there was nothing. It was totally silent save for noise from the street. It'd only been a few minutes since Sherlock had gone into the bathroom and John hadn't heard a thing since the tap was turned off.
"Sherlock?" he called as he walked down the hall to the bathroom. "Sherlock, you in there?" He tried the knob and found it unlocked. John saw Sherlock had left his towel on his bed and grabbed it; he didn't want to risk running into Sherlock naked.
"What John?" Sherlock's voice came through, sounding exasperated, as if John had interrupted something extremely important.
"What are you doing in there? It's too quiet." John said.
"I'm taking a bath like you insisted I do. Honestly John, I didn't need one."
"Yes, you did. Sherlock, you were starting to smell and Lestrade didn't want to stand next to you. Also, you forgot your towel..." John said as he stepped in and tried comprehending the scene in front of him. The shower curtain was pulled back, revealing Sherlock in a near-overflowing tub, all his clothes still on. His nose was just barely above the water and he was scowling at his knees. Four rubber ducks floated around, and John wondered where Sherlock had gotten them.
"Sherlock, you really don't like taking care of yourself while on cases, do you?" John sighed.
"You're the one who forced me to do this. I was adequately clean before, John."
"No, you weren't. Sherlock you didn't even take off your clothes-"
"John?"
"Yes?"
"I require another duck."