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In Memory, when Miles Vorkosigan begins to realize who he is as Lord Vorkosigan (he'd shunted all of his energies into Admiral Naismith for years), one of his first actions is to take a hot shower, "to scrub out the unpleasant, lingering scent of shame." He even explicitly compares it to a baptism. He then dresses, for the first time, in full Vor Lord regalia, and begins on the path that would become his future. It's practically Redemption in the Shower.
In The Other Boleyn Girl, following her bloody and painful miscarriage of the King's son (basically the main reason she's Queen), Anne orders a bath be drawn up for herself, making the water so hot her skin flushes red. Her sister Mary (the narrator) remarks on the usual similarities to baptism. After this thorough cleaning, Anne puts on a dazzling silver and white gown to emphasize her innocence and purity.
When Harry asks after Quidditch team captain Wood after the Gryffindor team loses their first match in Prisoner of Azkaban, the twins admit that he is still in the showers, and joke (we hope) that they think he's trying to drown himself. Add to this that they'd been playing in a thunderstorm, and were all already soaked.
The Dresden Files: After the disastrous ball at Bianca's Michael finds Harry Dresden huddled under the spray of his unheated shower suffering from angst and the early stages of hypothermia.
Iris of The Ultra Violets spends a traumatic couple of hours in the shower, trying to turn her now purple hair back to blonde—only to find out it's permanent. Gene modifying goop does that.
In Bloodsucking Fiends, newly-turned vampire Jody takes a shower and cries for her lost humanity; she also flashes back to a similar incident when she lost her virginity.