Santorini's beaches are the part visitors get most wrong. The island is a volcano, and its beaches behave like volcanic beaches — not like the Cyclades postcard.
What volcanic sand means
It is dark, and dark absorbs heat. Perissa and Kamari in the middle of a July day are genuinely too hot to cross barefoot. Sandals or beach shoes are not a refinement.
It shelves steeply. The water gets deep quickly, which suits swimmers and is worth knowing with small children.
The caldera side has no beaches at all. It is a cliff. Visitors who book Oia or Imerovigli expecting to swim from the shore are booking a view, not a beach — the swimming is on the far side of the island.
The main beaches
Perissa and Perivolos — a long continuous stretch of black sand on the southeast coast. Perivolos has the beach clubs; Perissa is slightly cheaper and calmer. Both have full facilities.
Kamari — the other side of the same headland, more developed, with a promenade and more hotels. Similar sand, similar water.
Between the two rises Mesa Vouno, with Ancient Thera on the ridge — walkable from either side.
The unusual ones
Red Beach, near Akrotiri — a cove under oxidised red cliffs, and the most photographed on the island.
Access is by boat from Akrotiri or on foot over a short, loose cliff path. The land route has been subject to rockfall closures and warning signs at various times — check current access rather than assuming, and take the warnings seriously.
White Beach, adjacent, reachable only by boat.
Vlychada — the most striking, beneath wind-eroded pale cliffs that look sculpted. Quieter than the main beaches.
Koloumbos, remote and often naturist.
Where to swim from a boat
The caldera sails stop at the hot springs off Nea Kameni — sulphurous warm water where the boat anchors and you swim across. It stains light-coloured swimwear, which nobody mentions until afterwards.
Thirassia, the small inhabited island across the caldera, has a quiet harbour and a beach, and almost no visitors.
Getting to them
Buses from Fira reach Perissa, Kamari, Akrotiri and Oia, and are cheap.
An ATV or small car makes the beaches and Pyrgos much easier. Roads are narrow and busy in summer.
The beaches are on the opposite side of the island from the caldera villages, which is a 20–30 minute drive.
Where to stay for beaches
Perissa, Perivolos or Kamari — beach access, considerably cheaper than the caldera, and a bus to Fira.
Caldera villages — the view, the sunsets, the prices, and no beach.
Splitting a stay between the two sides works well on a trip of five nights or more.
Season
Swimmable roughly June to October, with September the best combination of warm sea and thinner crowds.
The meltemi wind in July and August makes some beaches choppy and can close boat trips — the east coast beaches are more sheltered on windy days.