Zakynthos Glass-Bottom Boat Tour: Turtle Island & Keri Caves

Turtle Island tour: marine life watching, swimming, and limestone cave exploration

A half-day glass-bottom boat tour of Zakynthos that departs from Agios Sostis Harbour or includes hotel pickup, taking you to Turtle Island and Keri Caves with a live English-speaking guide and captain. The boat's glass bottom lets you watch sea turtles and the sea floor without getting wet, though you can jump in to swim at Turtle Island and the caves. Bottled water and liability insurance are included; bring a camera and snorkel if you want to use them.

Step-by-step itinerary

Zakynthos glass-bottom boat cruise

• Board glass-bottom boat
• Cruise along Keri Caves
• Swim at Keri Caves
• Visit Marathonisi Island
• Spot sea turtles at Marathonisi
• Swim near sea turtles
• Explore Cameo Island

The Experience

The boat leaves from Agios Sostis Harbour or picks you up from your hotel, depending on which option you choose. Once aboard, the glass bottom becomes your window into the Ionian Sea—loggerhead sea turtles move through the water below, and the sea floor comes into view without you needing to leave the deck. The air-conditioned cabin keeps you comfortable between stops.

Turtle Island (Marathonisi) is a heart-shaped island famous as a nesting ground for endangered Caretta caretta sea turtles. You'll spot them from the boat, and if conditions allow, you can swim in the turquoise water alongside them. Keri Caves sit at the base of dramatic limestone cliffs and are only reachable by boat—the water inside shifts between electric blue and deep shadow as the boat glides through the narrow openings. This is where most people jump in for a swim, the water so clear you can see the rock formations below.

The tour also passes Cameo Island, a small private island near the harbor connected by a wooden footbridge, known for its romantic setting. Between stops there's time to take in the coastline and photograph the cliffs. A captain and guide lead the whole journey and speak English throughout. Bring a snorkel if you have one—the water at both swimming stops is clear enough to use it, though snacks aren't provided on board.

What’s included

• Bottled water.
• glass-bottom boat ticket.
• air-conditioned cabin.
• live English-speaking guide and captain.
• liability insurance.
• hotel pickup (on the hotel transfer option) or meeting point at Agios Sostis Harbour (on the port option).

Good to know

Easy physical levelPets welcomeInfants must sit on laps

Operated by Happy Days Zante

Is this one for you?Choose the hotel pickup option if you're staying at a major resort and want to skip the drive to the harbor; choose the port meeting point if you're staying near Agios Sostis or prefer to arrange your own transport there. Either way, the glass bottom means you see the turtles and caves without needing to snorkel or dive—you can stay dry the whole time if you prefer, or jump in at the two swimming stops.

Traveler reviews

4.41★★★★★★★★★★

97 verified traveler reviews

5 ★67

4 ★15

3 ★8

2 ★2

1 ★5

Read all the reviews ›

Top questions

What exactly can I see through the glass bottom of the boat?

The glass-bottom boat lets you watch sea turtles and the sea floor of the Ionian Sea without leaving your seat. You'll see marine life and rock formations as the boat cruises, and the view is clearest in the shallower waters near Turtle Island and inside Keri Caves.

Can I swim with the sea turtles at Turtle Island?

Yes, you can jump into the water at Turtle Island and swim. Loggerhead sea turtles live in these waters, and you may encounter them while swimming, though sightings depend on conditions on the day you go.

How do I get to Keri Caves if they're only accessible by boat?

Keri Caves sit at the base of tall limestone cliffs on the south coast of Zakynthos, and the glass-bottom boat takes you directly to them. The boat glides into the cave openings, and you can swim in the water inside the caves—it's one of the main swimming stops on the tour.

Is hotel pickup included, or do I have to meet at the harbor?

You choose at checkout: one option includes pickup from major resorts in Zakynthos, and the other option meets at Agios Sostis Harbour. Both options include the same boat tour, guide, and swimming stops.

What should I bring on this tour?

Bring a camera to photograph the coastline and caves, and a snorkel if you have one—the water is clear enough to use it at both swimming stops. Bottled water is provided on board. Snacks are not included, so bring any food you want to eat during the three to five hours.

Are there age or fitness limits for this tour?

The tour suits all physical fitness levels. Infants must sit on an adult's lap. Service animals are allowed on board.