I put it up in a ponytail holder and loop it so it is in a bun-like deal. I always shower after a bath so it is not a big deal if it gets wet.
Mine isn’t as long as some of our long-haired Dopers, but it is down to my bra strap.
I take a bath at least weekly. I often have my hair already washed before I take my bath, though I shower off quickly when I am done.
I pull my hair up into a high ponytail and pull a loop into it. Then I take half a dozen tiny hair clips (that look like stars!) and pin up any loose, long strands hanging around my face. Sometimes I jab a few bobby pins in there, whatever is nearby, often the decorative ones (though I have what seems to be thousands of regular brown ones, the only ones I can ever find when I take my bath are the bejeweled butterfly ones, or the little blue flowered ones, etc).
My husband thinks it is adorable, so I keep doing it. 
But it serves a couple of practical purposes, besides keeping my hair dry, I usually do my weekly mud mask type garbage while I sit in the tub, and it keeps that gunk out of my hair.
Even better when you get back OUT of the bacth, flick out the butterfly clip and it all falls down your back again…mmm
My braids are butt-length again, never mind what it is when the hair is flying free.
I usually use an over-sized bandana to bind it on top of my head, either bath or shower, unless I intend to wash it along with everything else.