I second Sakura - on a sense of being convenient and surroundings.
as to ink: you really have to cover it up before you can use it - and even in wet rooms you're usually demanded to strip (my mom was sort of annoyed when she had to strip in a hotel wet room... she's like "that's not even a fake onsen - just water!), so you cant (technically) use it. I've been to hot tubs in Osaka/Tokyo where they ask people to cover tattoos up to use, but i dont remember which one(s) since it does not affect me (possibly hilton tokyo but i'm not sure).