Alan was sixty. His sex life with his wife had become almost non-existent. He didn't really know why. Alan would still want sex two or three times a week. He'd settle for once a week. But even this didn't interest his wife. They'd talked about it but she wasn't really interested and, although she said she'd try, it hadn't really improved. So Alan had accepted that that part of his marriage was largely over. But he still loved his wife. They had good times together and had a reasonably comfortable lifestyle. And so Alan coped, mainly by masturbating when the urge for sex got too much.
The other way Alan had begun to cope was by visiting a naturist spa. Alan and his wife had been going on naturist holidays for many years. Alan's wife was quite happy being naked among naked strangers. She was very clear that naturism was a non-sexual activity and got upset if anyone tried to blur the line between wholesome naturism and activities like swinging. A disastrous visit to the naturist/swinging venue of Cap D'Agde in the south of France had confirmed her beliefs. While she tolerated Alan going to the naturist spa, she would not join him, seeing it as slightly sleazy.
She was not entirely wrong in her belief. The spa had very strict rules banning amorous behaviour on the floor containing the saunas, steam rooms and hot tubs. But it also had an upstairs area with "rest rooms" into which staff did not venture. Their purpose was unambiguous. There were some small rooms with padded benches where two or three people could fit. And larger rooms with large padded areas where maybe ten or so people could fit. Some had lockable doors and some, including the largest area, had no doors.
Alan enjoyed being naked with others and he enjoyed saunas and steam rooms. And he also ventured upstairs. Sometimes, he'd be on his own or the only rooms in use would have locked doors. But, at other times, there would be other people there, either waiting for somebody to join them or involved in some sort of sexual activity.
Alan would watch, too nervous to join in. He figured that if people didn't want to be watched, they'd use a lockable room or, better yet for privacy, have sex at home.
Quite often, because of the imbalance in the numbers between the sexes using the spa, it would be men masturbating each other or performing fellatio. Alan would watch, at first out of curiosity. Until then, he'd never seen another man with an erection. You certainly never saw them at naturist venues (except, perhaps, Cap D'Agde). And he was surprised to find that he too was becoming aroused. He'd never thought about being attracted to men and he didn't think he was attracted now. But there was something about seeing men in this excited state that made him excited too.
On rare occasions, a woman would be present. She'd be actively engaged with two or three men. She might be sucking one man's penis, masturbating another while the third was fucking her. Two or three others would stand as near as they could get, watching and masturbating. Alan would watch, his penis pointing urgently upwards but he was too nervous to touch it or to join in. He'd have to go to a private room, lock the door and toss himself off to relieve his tension.