One rule, one stop

The dark swimsuit rule at the Santorini hot springs

7 min read

Wear a dark swimsuit you do not love. The hot springs at Palea Kameni are stained ochre by iron oxide rising from the seabed, and that iron binds to pale fabric. White and pastel swimwear comes out orange-brown, and it does not always wash out. Nothing else about the stop needs preparing.

Every operator on this island says wear something dark, and almost none says why. Here is why, what the water does to each fabric, and what to try if you already have an orange bikini in your case.

Why the water is that colour

The springs discharge into Agios Nikolaos bay on Palea Kameni, the older of the two volcanic islands in the middle of the caldera.

What comes up through the seabed is mineral-rich hydrothermal water: principally iron, with sulphur and manganese alongside it. The iron oxidises in the seawater and stays in suspension. That is what turns the bay rust-orange and makes it opaque, and why the stop smells of sulphur.

It is the same chemistry as rust on a white shirt, and it behaves the same way. Suspended iron oxide finds pale fibres, binds to them, and does not care that the swimsuit was new.

Published water temperature in the bay is roughly 30 to 35 °C. Treat that carefully: it comes from tourism sources, not an instrument reading. The ambient Aegean sits at about 20 to 25 °C depending on the month, so the honest description is noticeably warmer than the sea, not a hot bath.

The numbers

What the water does to what you are wearing

The first column is what goes in the water with you. The middle column is what comes out.

What you are wearing	What the water does	What we would do
White or pastel swimsuit	The worst case: orange-brown marks that survive repeated washing. santorinidave.com reports that the mineral water discolours pale fabric (seen 25 August 2026).	Leave it in the room. This is the whole rule.
Dark synthetic swimsuit	Little or nothing visible. Polyester and nylon hold the colour they were dyed.	Wear this.
An old swimsuit of any colour	Whatever happens, happens, and you have already decided you do not mind.	Also fine, and better than a new dark one.
A pale rash vest or cover-up	The same chemistry, over a much bigger area of fabric.	Take it off on deck before you go in.
Light cotton	The most absorbent thing you can put in that bay, and the slowest to give the iron back.	Do not swim in it.
A white towel	Meets the water second-hand, off your skin and hair.	Use one of ours. They are on board, included, and they meet this water every cruise.
Silver or plated jewellery	There is sulphur in the water. Guide sites advise taking jewellery off before the swim; we have not tested it ourselves.	Stow it in a bag before you go down the steps.
Bleached or very blonde hair	Tinting is reported by guests and by guide sites. We cannot tell you how likely it is.	Soak it in fresh water first so it is already full, and rinse it straight after.

It is opaque, it smells of sulphur, and it is the reason this stop needs one sentence of warning and nothing else. The rest of the packing question is in what to wear and bring.

How it works

If you have already stained something

What we tell guests who ask on the way home. It is laundry advice, not a guarantee: iron marks are difficult and sometimes permanent.

Rinse it before it driesThe best moment is on the boat, in fresh water, while the mineral is still loose. A stain that dries in the sun on the way back has had hours to set.
Wash it cold, on its ownCold water and ordinary detergent, and nothing pale in the drum with it. Hot water is a good way to fix a mark you were trying to lift.
Do not reach for chlorine bleachHousehold bleach is not a rust remover. On iron marks it is more likely to set the colour than shift it, and it will do nothing kind to elastane.
Try a rust remover made for fabricProducts sold for rust and iron marks on clothing are the right family of thing. Test a seam first. That is general rust advice, not something we have trialled at sea.
Then accept itFirst-hand accounts report marks that survive repeated laundering. If the swimsuit matters to you, the fix was leaving it in the room.

What the swim is actually like

The second most common regret at this stop is not a stained swimsuit. It is an expectation of a hot tub.

Question	Answer
How hot is it?	Warm, not hot. Roughly 30 to 35 °C published, against a sea of about 20 to 25 °C. You notice the change; you do not gasp at it.
How do you get in?	From the boat. We anchor off — there is no jetty at Palea Kameni and no shallow entry — so you go down the swim ladder into cool, deep water and swim in.
How far is the swim?	Community reports and guide sites put it at roughly 30 to 50 metres. We have not measured it, so treat that as the market's number rather than ours.
Do I need to be a confident swimmer?	Yes. Guide sites say the same, because there is no wading in from a beach. If you are not confident, this is the stop to sit out, and nobody will comment.
What does it smell of?	Sulphur. Faint on deck, obvious in the water.
Can you see anything underwater?	No. The iron in suspension makes it opaque. Snorkelling here is pointless — save the mask for Mesa Pigadia.
Can I skip it?	Yes. Stay on deck and the boat carries on to lunch either way. Several guests on any cruise never get in.

Your exact meeting point and the day's running order are confirmed with your booking. The captain reorders the stops when the wind asks him to.

One thing we will not tell you

There is no official instrument reading for the temperature of these springs, and no official measurement of the swim distance. Both numbers here come from tourism and community sources, and we have marked them as such.

Ready when you are

The springs are on the day cruise

Five hours, €100 per person, the crater swim on every departure and Palea Kameni whenever the sea allows. Send us your date and how many of you there are. Pack the dark swimsuit.

Check availability & book

Call the harbour office+30 698 977 1888

Common questions

Do Santorini's hot springs stain your clothes?

Yes, pale ones. The iron and sulphur leave an orange-brown tint on light swimwear, and first-hand accounts report marks that survive repeated washing. Wear something dark or old, and rinse and wash it as soon as you are back. The sooner it is washed, the less the iron binds.

What should I wear to the hot springs?

A dark or older swimsuit you do not mind discolouring. Leave the white bikini and the pale board shorts in the room, and take off silver jewellery before you go in. A dark rash vest is a good call too, since the swim is in open water with the sun overhead.

Are the Santorini hot springs actually hot?

No. The published figure for the bay is roughly 30 to 35 degrees against a sea of about 20 to 25, so it reads as noticeably warmer rather than hot. That figure comes from tourism sources, not an instrument. On a windy day the bay mixes and the difference is smaller.

How do you get hot-springs stains out?

Rinse in fresh water before it dries, then wash cold and alone with ordinary detergent. Skip chlorine bleach, which tends to set iron marks rather than lift them, and try a rust remover made for fabric instead. Sometimes none of it works, which is why we say wear dark.

Should I take my jewellery off?

We would. There is sulphur in the water, and guide sites advise removing silver and plated pieces before swimming at the springs. We have not tested it, so we cannot tell you how bad it gets. Rings are also easy to lose off a swim ladder in deep water.

Why is the water at the Santorini hot springs orange?

Iron. Hydrothermal water seeps up through vents in the seabed of Agios Nikolaos bay, carrying iron with sulphur and manganese. The iron oxidises and stays suspended, which turns the bay rust-orange and makes it opaque. That same iron is what marks a pale swimsuit.

Santorini Boat Tour - Water Taxi is a catamaran cruise and water taxi operator based in Fira, Santorini.

Updated August 2026