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Explore Zakynthos’ stunning marine park with a glass-bottom boat tour to see turtles, caves, and Marathonisi Island—perfect for nature lovers and photo enthusiasts.
Agios Sostis: Marathonissi, Keri Caves, and Turtle Spotting – A Detailed Review
Imagine gliding across crystal-clear waters, spotting ancient caves, and catching a glimpse of endangered turtles in their natural habitat—all in just a few hours. This 3-hour boat tour from Laganas offers a chance to experience some of Zakynthos’ most iconic sights without breaking the bank. It’s a well-rated trip that combines scenic beauty, wildlife encounters, and authentic island vibes.
What we love most about this experience is the opportunity to see loggerhead turtles up close in the wild—a rare chance that many travelers cherish. The glass-bottom boat adds an extra layer of excitement, allowing clear views beneath the surface without needing snorkel gear. Plus, the stops at Keri Caves and Marathonisi Island are stunning photo moments and offer a true taste of Zakynthos’ natural beauty.
However, a potential consideration is that swimming inside the caves is not permitted, which might disappoint some adventure seekers wanting to explore limestone caverns more thoroughly. Also, the beach on Marathonisi is small and protected, so if you’re after a typical sunbathing spot or longer beach time, you might find this stop a bit limited.
This tour is ideal for travelers who appreciate nature, want to see sea turtles in their environment, and enjoy short, scenic excursions. It’s perfect if you’re looking for a value-packed experience that combines wildlife, beautiful scenery, and relaxed island exploration.


Starting from Agios Sostis harbor in Laganas, the tour begins with a welcoming vibe, with the captain—whose engaging commentary and friendliness earn praise from reviews—greeting guests and setting the tone for a relaxing, fun-filled trip. You’ll find the boat equipped with shaded seating if you prefer to stay cool, or a rear sundeck if you’re eager to soak up the sun.
The first stop is at the Keri Caves, which are only accessible by boat. As you approach, the limestone cliffs tower above the water, illuminated by the sunlight filtering through the blue, creating an almost surreal atmosphere. The caves are particularly striking at Oasi Bay, where the crystal waters invite you for a refreshing swim. Several reviewers, like Naomi, highlighted the dramatic scenery and the delight of seeing turtles in their natural environment—an experience that feels both rare and genuine.
Many guests comment on the quality of the guide, mentioning how knowledgeable and enthusiastic the captains are. Santiago said, “The guide was very fun,” which adds a personal touch to the journey. The turtle sightings are a definite highlight, with reviews from early July noting that turtles often leave the area as eggs hatch, but some still manage to be spotted, making it a bit of a wildlife lottery.
The swim stop at Oasis Bay, close to the caves, is a favorite moment for many. The shallow waters are perfect for snorkeling and relaxing, and a few reviewers appreciated the chance to snorkel in the calm, shallow waters. Keep in mind, swimming inside the caves isn’t allowed, but the exterior views and water play make up for that.
Next, the tour heads to Marathonisi Island, often called Turtle Island, because it’s a breeding ground for loggerhead turtles. Approaching the island, you’ll see lush pine and oak forests, with the small beach area designated as a turtle nesting site. This protected environment is part of the National Marine Park of Zakynthos, so the beach is quiet and pristine, but only a limited section is accessible.
On the island, you’ll have free time to wander or visit the bar, where you can buy snacks, ice cream, or drinks. Reviewers like Babs and Nadia mentioned the short beach stop as a highlight, especially for snorkeling and relaxing in the shallow waters.
The overall duration of 3 hours means you get a taste of the best spots without feeling rushed, though some reviewers suggest that a longer trip might allow for more exploration. The boat’s price point of around $28 is quite reasonable, especially considering the wildlife and scenic beauty you’ll encounter.
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Multiple guests praised the knowledgeable guides and the beautiful scenery. Santiago shared, “We had an amazing time and the guide was very fun,” capturing the friendly, relaxed vibe of the tour. Naomi emphasized the incredible experience of spotting turtles in their natural environment, calling it “incredible” and “delightful.” Babs highlighted the snorkeling opportunity and the chance to see caves and islands, describing it as an “amazing day trip.”
One reviewer, Laura-Mdlina, pointed out that although turtle sightings are not guaranteed, the activity is still worthwhile for the stunning scenery and the caves. Several people appreciated how well-organized the trip was, with smooth departures and attentive crew members.

This tour offers a fantastic balance of wildlife observation, scenic beauty, and relaxed island time. It’s particularly suited to those who love wildlife, photography, and natural landscapes without the need for an intensive adventure. The small price point makes it accessible, and the short duration makes it easy to fit into a busy itinerary.
Even if snorkeling inside the caves isn’t allowed, the exterior views and the potential turtle sightings make this a memorable experience that captures the essence of Zakynthos’ marine environment. The friendly guides, clear explanations, and well-planned stops ensure you’ll get plenty of value for your money.

Is hotel pickup included in this tour?
No, the tour starts at Agios Sostis harbor, and guests need to meet there directly.
Can I purchase food and drinks on the island?
Yes, snacks, drinks, and ice cream are available for purchase at the Marathonisi bar during your free time.
How long is the boat ride?
The entire tour lasts around 3 hours, including stops for swimming, sightseeing, and the island visit.
Are snorkeling masks provided?
Snorkeling gear is not included but can be brought along—many guests find it helpful for exploring the shallow waters near the caves and island.
Can I swim inside the caves?
No, swimming inside the limestone caves is not allowed, but the exterior waters are perfect for a quick dip.
Is it suitable for children or families?
Yes, the trip’s gentle pace and focus on wildlife and scenery make it suitable for families, although young children should be supervised around water.
To sum it up, this boat tour from Laganas offers a marvelous peek into Zakynthos’ marine treasures—perfect for wildlife lovers, photographers, and anyone craving a scenic, authentic experience at a reasonable price. It combines the thrill of turtle spotting with the awe of the limestone caves and the charm of Marathonisi Island—an excursion that many travelers will cherish long after their trip ends.