This is a follow up to the technique I submitted here awhile ago.
In the shower I will keep the shower spray running and let the tub fill up a little. I angle the spray so it's as far down as it'll go. I lie down on my stomach in the tub facing away from the spray and adjust myself so the water is hitting my butt and my upper thighs. Now I will cross my arms underneath me and play with my nipples. While doing this I move my hips from side to side so the water isn't constantly spraying on the exact same area. After a bit of this I spread my legs and let the water spray against my lips while I continue to move my hips. Then after my arousal has gone up, I start humping my hips up and down so the water slides along my pussy and my mound and my clit bump the bottom of the tub. I continue on this until I reach orgasm, usually a few or more.
Now what I discovered a month ago is expanding on that technique. I brought my waterproof rabbit vibrator into the shower with me. I slide the dildo part of it up into my pussy, but instead of turning it so the little 'rabbit' vibe part was against my clit, I flipped it around and let that small part pop into my butt. I lie down on my stomach in the tub with the water spraying just like I mentioned above. Instead of spreading my legs, I hold my legs tight together and push my hips down against the tub. I turn the vibrator (both the part in the didlo and in the rabbit vibe) on high and let it do it's magic. I do play with my nipples like I mentioned while the vibe is doing it's thing. The first time I did this I came in less than 15 seconds and had four orgasms in less than a minute.
I try not to do this too much as I don't want to desensitize myself to how amazing it feels when I do it. So I do it about once, maybe twice a month and every time I orgasm hard and fast and I end up shaking in the tub.