Sundays are fun! That's because on Sunday, we take a situation you might find a female character to get a sexy nude scene... and put a male character in it while keeping it exactly as sexual! These are the only things I regard as NSFW, for the record, don't want the kids getting into sex.
One of the most common ways anime producers add revenue to their product is through Fanservice Posters. These depict the ladies of the show in some kind of sexy situation, and the most common way this is done is a bath scene. The purpose is pure Sex Sells, playing on the Otaku market's baser instincts and giving them softcore porn to use as they please, for their pleasure.
Enter Free! Eternal Summer. Free! is all about taking fanservicey swim team anime involving women in bikinis... and doing it with men instead, while maintaining the sexy. The women all get the ideal perfect female body with big hips and breasts, so the men get the ideal male body with muscles and smoothness. Since fanservice anime relies on the girls being lesbians to fuel more fantasy, Free! insinuates the guys are all gay behind the scenes to fuel its fantasy. It's probably perverted women's fantasy, given it does everything girls get and gives them the equivalent.
So what we have here is a Fanservice Poster of the Free! boys, putting them in the common bath scenario women go through. It's a perfect example of role reversal, and shows that male nudity isn't always humorous; it can be quite alluring, too if you do it right.
I mean, if you take what happens to a girl and do it to a guy, it's still sexy, right?