People ask for both and mean the same thing. Ice bath, cold plunge, cold immersion: one tub of cold water you get into on purpose. There is no technical difference and nobody in the room will correct you.
What actually varies between places is temperature, whether it is filtered, and whether it holds that temperature on a busy day. Those are the things worth asking about.
The number that matters
Ours sits between 3 and 8°C, filtered continuously and temperature controlled, which means it is the same cold on a quiet Tuesday morning as on a full Saturday evening. A tub that started cold and has had fifteen people through it is a different proposition, and you can feel the difference immediately.
Below about 10°C you get the response people are chasing. Above 15°C it is a cool bath, pleasant enough, not the same thing.
One to three minutes, and that is the whole job
The most common mistake is treating it as an endurance test. It is not. The physiological response happens in the first minute or two, and staying in for ten does not multiply it. It just makes you cold and slightly miserable.
One minute is a real plunge. Three is a long one. If you are shivering hard after you get out, you overdid it.
The first twenty seconds
There is no way to make the entry pleasant. What you can control is your breathing.
Get in steadily rather than jumping. Breathe out as you go under, long and slow, and resist the gasp that wants to happen. The gasp reflex is automatic and it is what makes people panic. If you can push through the first twenty seconds without hyperventilating, your breathing settles on its own and the rest is manageable.
Some people count. Some people use a rhythm, four counts in through the nose, six out through the mouth. Both work because both give you something to do that is not thinking about the cold.
What it actually does
Cold narrows your blood vessels and triggers a sharp adrenaline response. That is where the alertness comes from, and it lasts well past the session, which is why people book an evening slot and then cannot sleep, or a morning slot and feel sharp until lunch.
For soreness, the evidence is more modest than the internet suggests. Cold after training reliably reduces how sore you feel, which is not quite the same as speeding recovery. Worth knowing if you are doing it for the muscles rather than the head.
There is also a worthwhile caveat: if you are lifting for strength or size, regular cold immersion straight after training may blunt some of the adaptation. Plunge on rest days or hours later if that is your goal.
Hot first, or cold first
Either. Most people go heat then cold, because the contrast is sharper and the warm body makes the entry easier. Some go straight into the cold at the start to get it over with.
What matters more is resting properly between rounds. Five to ten minutes doing nothing, so your body gets a chance to level out before the next round.
Where to do it in Hiriketiya
Ours is downstairs at Maha Sauna on Hiriketiya Beach Road, part of a circuit with the wood-fired barrel sauna, steam room and magnesium bath. Ninety minutes, LKR 6,000, water and towel included.
Come with the intention of getting in twice. The second one is always easier than the first, and that is the thing people remember.