Shower points to the setting rather than to any particular act: scenes filmed in or around a shower stall, a wet room or a bathroom with running water. Some material grouped this way is bathing on its own, while other material uses the shower simply as the place where a scene starts or ends. Related vocabulary that appears around this term, such as big cock, beard, blowjob or anal, refers to other aspects of gay material and carries no meaning about water or bathrooms. If you are after outdoor water settings like pools or beaches, those fall under separate terms rather than this one.