Keri Caves: The Sea Caves You Actually Swim In
The swim-in sea caves under Cape Keri in south Zakynthos: where they are, which harbour to use, swimming, snorkelling, diving and the Marathonisi pairing.
The Keri Caves are the island’s second cave system, and the one most visitors get wrong in the opposite direction from the Blue Caves: people assume they are the lesser version of the famous northern arches, when in practice they are the caves you spend more time inside. A run of limestone caves, tunnels and two rock arches under Cape Keri at the south-western tip of Zakynthos, they sit inside the National Marine Park, three hours from your hotel and back on a small boat, and almost every trip pairs them with Marathonisi — Turtle Island — and the Mizithres sea stacks.
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What the Keri Caves are
Cape Keri (also mapped as Marathia Cape) is the south-western horn of the island. Its seaward face is white limestone, undercut by the sea into a sequence of caves that runs for a couple of kilometres along the cliffs. Some entrances are barely wide enough to swim through; others take a whole boat. Two natural rock arches — the kamares — break the line; the larger one takes a boat at speed.
The water inside is the point: shallow over a pale seabed, so the light comes up from below and the caves glow a milky turquoise rather than the north’s electric blue. On a calm morning the boats nose inside, cut the engine, and you go over the side.
Keep three names straight, because listings use them interchangeably: Keri is the hill village; Limni Keriou is the harbour and resort below it, home to the local caiques and the dive centres; Agios Sostis, on the edge of Laganas, is where the big turtle-and-caves excursions leave from.
Where they are and how you get there
There is no path. The caves are reachable only from the water, so the practical question is which harbour.
| Departure | Where it is | Who leaves from here | Sail to the caves |
|---|---|---|---|
| Agios Sostis | The harbour at the western end of Laganas, 2.5 km from the resort | Most of the big turtle-and-caves excursions, speedboats, self-drive rentals | Across Laganas Bay via Marathonisi, ≈30–45 min |
| Limni Keriou | The harbour under Keri village, south-west coast | Small local boats, private charters, the dive centres | Round the cape, ≈10–20 min |
| Laganas beach / hotel pickup | Minibus to Agios Sostis | The pickup-inclusive trips | As Agios Sostis |
From Zakynthos Town, allow around half an hour by road to Limni Keriou and slightly less to Agios Sostis; from Laganas or Kalamaki both are minutes away. From the northern resorts the south coast is a 45-minute-to-an-hour drive each way, which is why most northern-based visitors take the trips with hotel pickup.
The boat trips, and what each format gets you
Almost every Keri Caves trip is a three-stop loop — Marathonisi, the caves, and the Mizithres or Cameo Island — with turtle spotting on the way. The differences are the boat.
Speedboat. Turtles, Marathonisi & Keri Caves Speedboat Tour is the reference product — $32, 3,297 reviews at 4.5, three hours from Agios Sostis with hotel pickup, and the captains take the boat inside the caves and through the arches. Our breakdown → The same operator’s Laganas Bay, Myzithres & Turtles trip at $35 swaps Cameo for a swim at Mizithres beach.
Glass-bottom boat. Turtles, Marathonisi & Keri Caves Glass-Bottom Boat Tour is the calm-water family option — $32, 2,907 reviews at 4.4, three hours, pickup within 10 km of Agios Sostis. Our breakdown → For a longer loop, the 4-hour Turtle, Keri Caves, Mizithres & Eros Cave trip at $47 adds the heart-shaped Eros Cave and the “Pisines” pools. Our breakdown →
Cheapest. Agios Sostis: Marathonissi, Keri Caves & Turtle Spotting is $29 — no pickup, and note its own terms: you swim at Oasis bay in the caves area, not inside the cave itself. Our breakdown →
The full comparison, including private boats, is on the Keri Caves tours page; the turtle-first version of the same decision is on Keri Caves + Turtle Island tours.
Swimming and snorkelling
This is where Keri beats the north. The Blue Caves are a look-and-photograph experience for most boats; the Keri Caves are a swim. Expect one or two swim stops in or beside the caves plus a longer one at Marathonisi, with the sea at around 25–26°C in July and August and comfortable from late May into October.
Snorkelling is good rather than spectacular: clear water, rock walls, small fish. Most shared trips do not include masks — the glass-bottom boat lists snorkel gear as an exclusion — so bring your own. Reef shoes matter more here than anywhere else on the island: the cave floors and the pebble coves are sharp limestone. Our packing list covers the rest.
Diving
Limni Keriou is the island’s dive hub, with several centres working the cape: the caves themselves, the two arches, reefs off the peninsula and the seabed around Marathonisi, all within a short boat ride of the harbour. If you have never dived, the Scuba Diving Experience with Underwater Photos ($181, minimum age 13) dives at Marathonisi and the Keri Caves after a shallow-water skills session, and the Small-Group Scuba for Beginners ($216, four students per instructor) adds a pool session first. Both leave from Agios Sostis. Leave at least 12 hours between a dive and a flight.
Keri Caves + Marathonisi + turtle spotting
The caves and the turtles are one product because they are one bay. Marathonisi sits two nautical miles off both Laganas and Keri, and the boats cross the National Marine Park to reach either. Loggerheads nest on the bay’s beaches from mid-May to August and are in the water from roughly May to October; you will usually see one, but no honest operator can promise it, and the park holds boats to about 15 m from a turtle and a slow speed in the protected zones. Landing on Marathonisi is allowed in daylight only, on a 5 m strip at the water’s edge, with no umbrellas and a visitor cap.
Private boats and licence-free rental
The south coast is the easiest place on the island to run your own boat. Private Self-Drive Speedboat Rental No Licence from Agios Sostis is $146 for the boat (up to four people), fuel paid locally, with a canopy and a cool box — Marathonisi and the caves are within easy reach. Our breakdown → Licence-free hire is generally limited to 30 hp within three nautical miles of the coast; firms quote different figures, so confirm with yours.
With a skipper, Turtle Island and Caves Private Boat Trip is $276 for two people, three hours, with snorkel gear and underwater photos included. Our breakdown → All of these are compared on private boat tours.
Keri vs the Blue Caves
Choose Keri for swimming inside caves, a southern base, or turtles on the same ticket. Choose the Blue Caves for the signature electric-blue scenery and the Shipwreck Beach pairing. The full argument is on Blue Caves vs Keri Caves, and the island-wide version on north vs south boat tours.
Frequently asked questions
Can you swim inside the Keri Caves?
Yes — that is the main reason to choose them over the northern Blue Caves. Speedboat and small-boat trips enter the larger caves and stop for a swim inside or just outside them. Check the listing, though: the $29 Agios Sostis boat swims at Oasis bay in the caves area and states “no swimming inside the cave”.
Where do Keri Caves boat trips leave from?
Most leave from Agios Sostis harbour at the western end of Laganas, which is where the big turtle-and-caves excursions, speedboats and self-drive rentals are based. Smaller local boats, private charters and the dive centres leave from Limni Keriou under Keri village.
How long is a Keri Caves boat trip?
Three hours is the standard loop — Marathonisi, the caves and Cameo Island or the Mizithres. The Eros Cave version runs four hours, and private boats can be booked for two to six.
Are turtles guaranteed?
No. Loggerheads are in Laganas Bay from about May to October and most trips see at least one, but sightings depend on the day and the park rules keep boats at a distance. Treat the turtles as likely, not promised.
How much does a Keri Caves tour cost?
Shared boats start at $29 without pickup and $32 with it; the four-hour Eros Cave loop is $47. Self-drive boats start at $146 for the boat and skippered private trips at $276 for two.
Do I need a licence to rent a boat at Keri?
Not for the small engines the rental firms offer. The generally quoted limit for licence-free hire is 30 hp within three nautical miles of the coast, but operators quote different horsepower figures, so confirm with the one you book and bring a photo of your passport or driving licence.
Ready to book? Compare every south-coast trip side by side on the Keri Caves tours page, or check availability for the speedboat above — the most-booked way into the caves.
Pick Your Coast, Then Book
North for the Blue Caves and Shipwreck Beach, south for the Keri Caves and Turtle Island. Every trip we list has free cancellation on most dates — compare them side by side before you commit.
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