The caldera — the flooded volcanic crater that defines the island's shape — is visible from nearly everywhere on the rim, but actually swimming in it requires getting down to water level, which takes a little more planning than a beach visit.
How to get in
The primary access points are the old port below Fira (reached by cable car, steps, or donkey), from which small boats depart, and Ammoudi Bay below Oia, where a steep path leads down to a small rocky swimming area directly on the caldera. Both are deep, clear water — there's no beach or gentle slope, just a jump or ladder into open sea.
The hot springs
The most popular caldera swim is via a boat trip to the hot springs near Palea Kameni, where volcanic activity warms the sea to noticeably above ambient temperature — a rusty-orange mineral tinge colours the water close to the vent. It's accessible primarily through volcano boat tours (see our boat tours guide) rather than independently.
What it's actually like
The caldera is deep — very deep — and open to significant current, so it's not a relaxed beach paddle. The water is clear and the setting is extraordinary. Ammoudi Bay's swimming rocks below Oia are among the most memorable places to swim anywhere on the island: submerged lava formations, no sand, and the caldera cliffs above you. It requires a reasonable level of swimming confidence and is not ideal for young children or less confident swimmers.
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