He isn't at all upset about how they must position themselves, and he dips his mouth to kiss the back and side of Watson's neck, tenderly. Snaking his arm around Watson, he plucks the sponge out of his hands.

"Allow me," he murmurs, then more lightly, "it is my fault, after all." He runs the sponge over Watson's chest, able to tell what he's doing without needing to see Watson's front at all. To have him so well memorized gives Holmes a sense of accomplishment.