I'm a frequent floater. It wouldn't have any direct benefit for your back. However, the peacefulness you can find in a float would have an indirect impact. Without going supernatural on you, I can tell you that it has some of the same physiological effects as meditation -- lowered heart rate and lowered breathing in particular. You can also focus your mind wonderfully -- I've had several breakthrough thoughts, mostly on personal stuff, but a few mental solutions to interpersonal work stuff.
You may want to investigate the multi-mode introductory specials offered by Evolve Cryo Wellness (S. Lamar) and a few other spas around town. This is a great way to experiment on your body to see what works for you. For instance, for $100 in one visit of an hour or two, you can experience some combination of:
- cryo (freezing, also used by athletes to promote healing);
- vertical hang (upside down in a frame, if you've got doc's clearance for your back);
- massage (legit);
- acupuncture;
- huffing pure oxygen;
- with different combinations of those, depending on the spa.