Spa vs Hot Tub:
What’s the Difference?

Whats the difference?

In practical terms, the biggest difference usually comes down to how they are designed, how they are built, how they feel to use and what role they play in an outdoor space.

A traditional spa is generally a moulded, engineered product focused on jets, seating positions and hydrotherapy features. A hot tub is typically a simpler, more immersive bathing experience, often with a deeper tub, more natural materials and a stronger emphasis on heat, relaxation and the surrounding environment.

What is a spa?

In New Zealand and Australia, the word spa commonly refers to what is sometimes called a spa pool. These are usually self-contained units made from moulded acrylic, fibreglass or composite materials.

• They typically include:
• Built-in seats or loungers
• Multiple hydrotherapy jets
• Pumps and filtration systems
• LED lighting
• Control panels
• Insulated cabinetry
• Covers and heating systems

The defining feature of most spas is the jet system. Water is pumped through a network of jets positioned around the seats, often targeting areas such as the back, shoulders, calves and feet. Some models may have dozens of jets, different massage settings and individually shaped seating positions.

For many people, that is exactly what they are looking for. A spa is generally designed as a feature-rich hydrotherapy system where the machinery and internal layout play a major part in the experience.

The value of doing something difficult

“It has great physiological and mental benefits. I do it every day... wow, it sucks. But you get out and you're like, 'This is amazing.' You get out and immediately you get this rush of endorphins, this rush of norepinephrine, and dopamine, and it lasts for hours." - Joe rogan

Not every benefit of cold water is easily captured in a laboratory. Part of the appeal is behavioural.

Getting deliberately into cold water requires you to make a small decision to be uncomfortable. Once in, the immediate goal becomes remarkably simple: control your breathing, stay composed and remain present.

Yesterday’s emails suddenly feel much less important.

Many regular cold-water users describe this as a mental reset. There are plausible physiological mechanisms behind some of those experiences, but scientific evidence for sweeping claims around mood, mental health and cognition remains limited.

The PLOS ONE researchers specifically cautioned that many popular claims surrounding cold-water immersion have moved faster than the underlying research. Their review found promising results for some measures of stress, sleep and quality of life, but not strong evidence for many of the broader claims often associated with cold plunging.

Cold water does not need to be a miracle treatment to be worthwhile. Sometimes doing something challenging, getting outside and emerging feeling very awake is reason enough.

What is a hot tub?

The term hot tub has a broader meaning, but traditionally it refers to a deep tub filled with heated water that is designed primarily for soaking.

The original hot tubs were often round timber tubs heated by wood-burning stoves. Modern versions can use electric heating, filtration and contemporary construction methods while retaining the simplicity of the original idea. Instead of being built around moulded seats and large numbers of jets, a hot tub often prioritises:

• Deeper water
• Open seating
• Natural body movement
• Heat
• Quiet
• Social connection
• The view and surrounding landscape

A hot tub is less about sitting in a predetermined position and more about immersing yourself in the water. This distinction is important because the experience can feel very different.

A spa can feel like an appliance

There is nothing wrong with appliances. They are designed to perform a specific job well.

But aesthetically, many traditional spa pools are clearly pieces of equipment. You can see the acrylic shell, plastic fittings, control panels, jets, headrests and cabinet. The spa is an object that has been placed into the environment.

A hot tub often aims to feel more integrated. Natural timber, stainless steel and simpler forms can allow it to sit more comfortably alongside decks, stone, planting and architecture. This is particularly relevant in landscapes where the surroundings are a major part of the experience.

A mountain view, native garden or remote lodge setting does not necessarily need more visual noise. Sometimes the best product is the one that allows the location to do most of the work.

Do hot tubs have jets?

They can.

Modern hot tubs do not have to follow the purely traditional format. Some incorporate hydrotherapy jets, filtration, electric heating and sophisticated temperature controls while keeping a simpler internal layout.

This is where the distinction between a hot tub and a spa becomes less absolute. There is no international rule that says a product with jets becomes a spa or that a hot tub must be made from timber.

These are descriptive categories rather than strict technical definitions. The better question is not necessarily, "Does it have jets?" It is, "What was it designed to feel like?"