Hi Badger,
I've just started using a hydromax Bathmate as I had a prostatectomy in July. Not had a full erection yet with it as I'm struggling to get used to it, but it definitely got some blood moving to the desired spot.
Used in both shower & bath 3 times in total, hope I'm more successful with it.
It's for a flaccid penis to get a erection, to keep the erection think you'll need a cock ring.
Hope helps