so if you feel like you want some depth and have a condom kicking around grab the plunger stick it to the shower (clean plunger obviously) and start rocking- thats what i do
Not entirely sure if it's a good idea to stick something up there that's not specifically designed to go there, you know what I mean? Hell, i've heard some stories of people fucking up the tissue down their from literally using standard dildos be careful man, dont want that to happen to anyone
I suggest getting a plastic hair brush with a rounded-off/phallic looking handle and then lube it up with some body gel (I do this nearly every time I decide to take a bath, I of course, make sure that my anus is clean as possible before doing it).