The National Marine Park of Alonissos and the Northern Sporades is the largest protected sea area in Europe, set up to safeguard the Mediterranean monk seal. In 2020 it became the site of Greece's first underwater museum: a fifth-century BC merchant ship off Peristera that sank carrying some 4,000 amphorae, most of which still lie in stacked rows across the seabed at 22 to 28 m. Guided dives on the wreck run in season, with the rest of the park offering quiet reef and wall diving.
About diving in Alonissos & the Peristera Wreck
A day here is built around one boat trip. Operators run from Patitiri and the smaller harbours on Alonissos, cross to Peristera for the museum dive, then move to a sheltered reef such as Agios Petros for the second tank. The wreck dive is guided throughout, booked ahead and run to a fixed plan on a protected archaeological site, so there is no wandering off on your own and nothing is touched or lifted.
The wreck reads as a cargo field rather than a ship. What you swim over is the load itself: thousands of amphorae from a fifth-century BC merchantman, still stacked in the rows they were stowed in and spilling down a mound between 22 and 28 m. With 20 to 40 m of visibility you take in the whole spread on the descent, then work along it slowly. It is a looking dive rather than a swimming one, and at that depth the bottom time goes quickly.
The rest of the park is quiet, low-traffic rock diving: reef slopes, short walls and small caverns, with ancient pottery scattered in shallow bays like Kokkinokastro. The water is clear and the current mild, so the difficulty sits in the depth and the certification bar rather than in the conditions. It suits divers with Advanced or around thirty logged dives who come for the archaeology and the protected setting, and who can work around a short, weather-dependent season.
Best time to dive Alonissos & the Peristera Wreck
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Season | Off-season | Off-season | Off-season | Fair | Good | Prime | Prime | Prime | Prime | Good | Off-season | Off-season |
| Sea surface | 15°C59°F | 15°C59°F | 14°C57°F | 15°C59°F | 18°C64°F | 23°C73°F | 26°C79°F | 27°C81°F | 25°C77°F | 22°C72°F | 19°C66°F | 16°C61°F |
| Daytime high | 17°C63°F | 17°C63°F | 19°C66°F | 23°C73°F | 27°C81°F | 31°C88°F | 33°C91°F | 31°C88°F | 30°C86°F | 26°C79°F | 22°C72°F | 18°C64°F |
| Rain | 80 mm3.1 in | 79 mm3.1 in | 71 mm2.8 in | 43 mm1.7 in | 25 mm1.0 in | 37 mm1.5 in | 19 mm0.7 in | 26 mm1.0 in | 60 mm2.4 in | 72 mm2.8 in | 66 mm2.6 in | 92 mm3.6 in |
| Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|
| Off-season | Off-season | Off-season | Fair | Good | Prime |
| Sea surface | |||||
| 15°C59°F | 15°C59°F | 14°C57°F | 15°C59°F | 18°C64°F | 23°C73°F |
| Daytime high | |||||
| 17°C63°F | 17°C63°F | 19°C66°F | 23°C73°F | 27°C81°F | 31°C88°F |
| Rain | |||||
| 80 mm3.1 in | 79 mm3.1 in | 71 mm2.8 in | 43 mm1.7 in | 25 mm1.0 in | 37 mm1.5 in |
| Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|
| Prime | Prime | Prime | Good | Off-season | Off-season |
| Sea surface | |||||
| 26°C79°F | 27°C81°F | 25°C77°F | 22°C72°F | 19°C66°F | 16°C61°F |
| Daytime high | |||||
| 33°C91°F | 31°C88°F | 30°C86°F | 26°C79°F | 22°C72°F | 18°C64°F |
| Rain | |||||
| 19 mm0.7 in | 26 mm1.0 in | 60 mm2.4 in | 72 mm2.8 in | 66 mm2.6 in | 92 mm3.6 in |
2011–2025 averages. Sea surface: NOAA Coral Reef Watch, measured at the surface, so deeper water can run colder. Daytime high and rain: NASA POWER.
The underwater museum and most operators run May–Oct only; meltemi winds can close the exposed Peristera site in midsummer.
Best months: June, July, August, September
Alonissos water temperature and weather by month
The sea surface runs from 14 °C (57 °F) in March to 27 °C (81 °F) in August. It is 24 °C (75 °F) or warmer from July to September. Most rain falls from September to March, peaking at about 90 mm (3.5 in) in December; July and August are the driest. Daytime highs reach 33 °C (91 °F) in July and drop to 17 °C (63 °F) in January. The coldest water here is about 14 °C (57 °F), so pack a 7 mm suit with a hood, or a semi-dry.
Dive types & marine life
The park was created for the Mediterranean monk seal, but seals are seen far more often from the boat than underwater. Below, expect dusky grouper along the reef edges, octopus and cuttlefish over the rubble, nudibranchs on the rock, and barracuda and fish shoals through the June–September peak.
- Wreck
- Reef
- Wall
- Cave & cavern
- Seals & sea lions
- Groupers
- Barracuda
- Octopus & cuttlefish
- Nudibranchs
- Reef fish swarms
Best dive sites in Alonissos & the Peristera Wreck
Wall from 8 m to 30 m, with rock running on to 50 m
The shallow half of the cove, with its best rock at 8 to 20 m
Reef
One of the area's dive highlights, and an ideal night dive
Wall to 20 metres, then into the most famous cave on Alonissos
Cave & cavern
A 70 m cave passage with its mouth between 22 and 34 m
A sharp drop to 50 m with openings and cracks in the face
A boulder-strewn plain further offshore than the West side
Often ends in a small cave full of young fish
A drop-off from about 10 m to 33 m, then a seagrass bed
A longer wall than the North, hung with old fishing nets
Wall
Named for its nudibranchs, flabellinas especially
Wreck
Dubbed the Parthenon of Shipwrecks, and dated to 425-420 BC
Cave & cavern
A tunnel descent from 14 m down to 22 m past small pinnacles
Cave & cavern
A lit tunnel with windows out to the open water
A wooden hull at 22 m, found by following a sandy channel
Kokkinokastro
Red-cliffed bay on Alonissos with shallow reef and ancient pottery.
How to get to Alonissos & the Peristera Wreck
Alonissos has no airport: most divers fly to Skiathos and continue by ferry or hydrofoil through Skopelos, or sail from Volos, Agios Konstantinos or Mantoudi on the mainland. Patitiri is the main port and the usual base. All diving is by boat, and the museum dives and most centres run May to October only.
Photos from Alonissos & the Peristera Wreck
dronepicr · CC BY 2.0
Dive videos
Peristera Wreck, Alonissos - Greece · jp piov on YouTube
Plongée Alonissos épave Peristera, Scuba diving Peristera wreck Αλόννησος Ναυάγιο Περιστέρας @Triton · Je plonge en Grèce on YouTube
Photo credits
- Red cliffs and islet of Kokkinokastro above turquoise shallows, Alonissos by dronepicr, CC BY 2.0, via Wikimedia Commons
- Pine-covered cliffs and clear rocky shallows on the Alonissos coastline by dronepicr, CC BY 2.0, via Wikimedia Commons
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