Maybe I'm a little weird, but....

[California Dolphin]

The post mentioned they were 17 and 18 so it looks like a case of teenagers fooling around as usual.

Recalling my days in PE class in the 60s and 70s, I've seen everything in the way of erotic conduct, but nothing XXX. So what you're seeing is plain vanilla.

As long as there were no adults involved in the shower scene, there isn't anything unethical or illegal about consenting teenagers engaging in erotic behavior.