Sensory deprivation tank, flotation tank, isolation tank, float pod. 4 names, 1 piece of equipment, and a surprising amount of research behind it.
Here's the plain-English explanation: what it is, what actually happens in there, what the evidence supports, and what an hour inside feels like.
They're the same thing. The name changed as the technology did.
"Sensory deprivation tank" comes from the original 1950s research by neuroscientist John C. Lilly, who built the first tanks to study what the brain does with no external input. "Isolation tank" carried the same idea. "Flotation tank" and "float pod" are the modern terms, and they describe the experience better: today's pods are spacious, you control the light and the lid, and nothing about a modern session feels like deprivation.
The scientific literature usually calls it Flotation-REST (Restricted Environmental Stimulation Therapy), which is the term to search if you want to read the studies.
Your nervous system spends the day processing an enormous volume of input: gravity, temperature, light, sound, touch, the position of your limbs. A float pod removes nearly all of it at once.
The salt does the heaviest lifting. Around 400kg of dissolved Epsom salt makes the water so dense you float on the surface without effort, which takes every gram of load off the spine, neck and joints. Hold the water at skin temperature and the thermal boundary disappears too. Kill the light and the sound and there's almost nothing left for the brain to monitor.
What follows is a parasympathetic shift: out of the alert, scanning, sympathetic state and into the repair state. That's the whole mechanism, and it's why the effects show up in stress and sleep rather than in muscles alone.
The evidence is unusually good for a wellness modality, with a caveat worth stating up front: most studies are small, and the strongest data covers single sessions rather than long-term courses.
The most-cited modern study is Feinstein and colleagues 2018 (PLoS One), which measured significant reductions in anxiety, stress, muscle tension and blood pressure after a single 1-hour float, with the largest effects in the most anxious participants. Earlier Swedish work found lowered cortisol across courses of floats. A 2023 systematic review of Flotation-REST found positive effects on pain, stress, mental wellbeing and clinical anxiety, and limited effect on diagnosed sleep disorders specifically.
So: strong for stress, anxiety and pain. Promising and still developing for sleep and long-term outcomes. It's a wellness modality, not a medical treatment, and diagnosed conditions belong with a GP.
You shower, put in earplugs, and step into around 25cm of very salty water. Lie back and you float immediately, without trying.
The first 10 to 20 minutes are usually the busiest: your mind runs its normal loops, you notice your breathing, you wonder if you're doing it right. Then something settles. Most people describe losing track of where their body is, and time going strange. The hour tends to feel like 20 minutes.
Coming out, the world feels loud and bright for a few minutes, and calm in a way that's hard to describe. Plenty of floaters report the best sleep of their week that night.
You won't sink, and you can't drown by falling asleep: the salt keeps your face clear of the water, and plenty of people do fall asleep in there. The lid stays under your control and you can leave whenever you like, which is what settles most claustrophobia worries. If salt water gets in your eyes it stings, so keep a spray bottle and towel within reach (every centre provides them).
Don't shave right before a session and skip caffeine beforehand. Both are the most common first-float regrets.
Beyond Rest runs float pods in private rooms across 6 centres: Hawthorn East, Moonee Ponds, Collingwood and Prahran in Melbourne, plus East Perth and Wembley in Perth. Every session is a private room with your own shower, and first-timers start with a consult so the session suits what you're bringing in with you.
For an honest comparison of the other float venues in each city, see the best float centres in Melbourne and Perth.
A light-proof, sound-proof pod containing around 25cm of water saturated with roughly 400kg of Epsom salt, held at skin temperature (about 35.5C). You float effortlessly on the surface with almost no sensory input, which lets the nervous system shift into a deep parasympathetic state. It's also called a flotation tank, isolation tank or float pod.
Yes. "Sensory deprivation tank" and "isolation tank" are the original 1950s terms from John C. Lilly's research; "flotation tank" and "float pod" are the modern names for the same equipment. Research papers usually call it Flotation-REST.
The salt removes all load from the spine and joints, and the absence of light, sound and thermal sensation triggers a parasympathetic shift out of alert mode. Research measured reduced anxiety, stress, muscle tension and blood pressure after a single session (Feinstein 2018), and lowered cortisol across courses.
The salt density keeps you floating face-up with your face clear of the water, and many people fall asleep during a float without issue. The lid is under your control and you can get out at any time.
Typically $79-99 for a 60-minute session, with packs and memberships bringing the per-float price down. At Beyond Rest a single float is $89. See prices and memberships.
Most people feel something from a single session. For sustained change, a course of weekly floats over 4 to 8 weeks is the pattern with the best evidence behind it.
If you've read this far, the curiosity is the answer. Book a first float and find out what an hour of nothing does. Prices and memberships.