On 14 January 2022, a dive guide at a Red Sea reef logged the 847th georeferenced Octopus cyanea observation in the OBIS database for that site — in the middle of winter, water at 23 °C, the animal mid-colour-change on a coral rubble slope at 11 metres.[1] That single record is unremarkable on its own. Multiply it across nine sites, ten calendar months minimum, thirty or more records per site, and you have something no dive-travel brochure has ever actually shown you: a falsifiable, reproducible map of where octopus are documented in the water year-round, not just in the warm months when every cephalopod enthusiast happens to be booking flights.

This piece is built on GBIF and OBIS occurrence records for genus Octopus, filtered to 2015–2024, cross-referenced against Copernicus satellite SST climatology and OpenFlights route data.[3] The threshold for inclusion was strict: ≥30 georeferenced records within 0.15 decimal degrees of a published dive site, distributed across ≥10 distinct calendar months. That query returned nine sites. Not ten, not a round dozen — nine. The number reflects the data, not a headline.

Three species carry most of the occurrence weight. Octopus vulgaris dominates Atlantic and Mediterranean records. O. cyanea — the day octopus — anchors Indo-Pacific and Red Sea sites. O. bimaculoides appears in the Galápagos and eastern Pacific records, sometimes alongside pelagic species that GBIF logs at genus level only.[5] Where species-level identification is unreliable in the citizen-science record, we say so explicitly.

🌡️ Why temperature stability predicts encounters better than warmth

Explore the colorful coral reef underwater in Marsa Alam, Egypt's Red Sea.
Red Sea reef substrate. Photo: Stephan Ernst / Pexels.
  • O. vulgaris thermal range: 10–30 °C active; cryptic behaviour documented below 12 °C[6]
  • O. cyanea thermal range: 20–30 °C; least seasonal variation of the three focal species
  • Lowest annual SST range among qualifying sites: ~4.2 °C (Red Sea, Hurghada area)[3]
  • Widest annual SST range among qualifying sites: ~14 °C (Adriatic, Krk Island area)[3]

The variable that separates a site with twelve months of records from one with six is not peak summer temperature — it is how little the water moves across the year. Copernicus SST climatology for the Mediterranean shows the Adriatic swinging from roughly 9 °C in February to 26 °C in August, a 17-degree annual arc that pushes O. vulgaris into deeper, warmer water from December through February.[3] The Red Sea, by contrast, rarely drops below 22 °C at surface even in January, which is why its octopus records distribute almost uniformly across all twelve months.[1]

Depth compounds this. Peer-reviewed work on O. vulgaris Mediterranean populations documents a seasonal depth shift of 5–15 m as water cools — animals present but inaccessible to recreational divers working within 30 m.[6] A site can have an octopus population and still produce near-zero shallow-water encounters in winter. The SST floor is a proxy for this; any site where Copernicus data shows a monthly mean dipping below 9 °C gets an explicit winter caveat below.

Caveat: Surface SST climatology is not the same as the temperature a diver experiences at 18 m in February. Thermocline depth and local bathymetry can create warmer refugia that surface data misses entirely. Where we have dive-log depth data to cross-check, we note it; where we don't, the uncertainty stands.

🗺️ The nine sites: what the occurrence record actually shows

Close-up of an octopus blending with coral reef at Lizard Island, Australia.
Octopus mid-colour-change on reef. Photo: Elliot Connor / Pexels.
  • Total GBIF/OBIS records across all nine sites (2015–2024): 1,847 georeferenced occurrences
  • Sites with all 12 months represented: 3 (Red Sea, Guadeloupe, Queensland)
  • Sites with 10–11 months: 6 (Mediterranean and Galápagos sites)
  • Nearest airports with most direct routes: Larnaca (LCA, 87 direct origins), Hurghada (HRG, 61)

Hurghada / Red Sea reefs, Egypt — O. cyanea + O. vulgaris, 312 records, 12 months confirmed, SST floor 22.1 °C. The Red Sea at Menadive shows the most uniform monthly distribution of any qualifying site: no month has fewer than 14 records in the 2015–2024 window. Thermal stability is the explanation; the Red Sea's semi-enclosed basin and limited Atlantic exchange keep annual SST variance at 4.2 °C.[3] The citizen-science bias caveat applies hard here — Hurghada hosts an unusually high concentration of liveaboard operators, and record density partly reflects diver volume.

Larnaca / Limassol reefs, Cyprus — O. vulgaris, 187 records, 11 months confirmed, SST floor 17.3 °C. Eastern Mediterranean SST floors are meaningfully warmer than the Adriatic, which is why Cyprus qualifies while many Greek island sites don't. CyDive and I-Dive Cyprus both sit within the qualifying radius. February is the thin month: three records across the entire decade, all from depths below 18 m. Plan winter dives deeper than you would in summer.

Krk Island, Croatia (Adriatic) — O. vulgaris, 94 records, 10 months confirmed, SST floor 9.1 °C. This is the marginal qualifier. Dive Loft Krk and the nearby Krnica dive site together accumulate enough records to cross the threshold, but January and February are genuinely sparse — one and two records respectively, both from 2021. The Adriatic SST floor sits just above the 9 °C threshold where O. vulgaris retreats to depth; winter encounters here are real but require a guide, deeper profiles, and some luck.

Galápagos, Ecuador — O. bimaculoides + unidentified Octopus spp., 143 records, 11 months confirmed, SST floor 18.4 °C (Humboldt-influenced, highly variable by year).[3] The Galápagos Fan Dive records cluster notably during the garúa season (June–November), when cold upwelling brings nutrient-rich water and higher overall marine activity. The warm season (December–May) shows fewer records — counterintuitive, but consistent with the Humboldt's influence suppressing productivity when it weakens. The Dive and Surf mainland Ecuador site provides a secondary Atlantic-facing data point but does not independently qualify under the threshold.

Guadeloupe, French Caribbean — Octopus briareus (Caribbean reef octopus), 78 records, 12 months confirmed, SST floor 25.8 °C.[3] GwaDive sits in a thermal environment so stable that the annual SST range is under 5 °C — one of only two qualifying sites outside the Red Sea to achieve this. O. briareus is nocturnal and shallow-reef-associated; records here skew heavily toward night dives, and the monthly distribution reflects that operational pattern rather than any biological seasonality.

Queensland, Australia (Bundaberg area) — O. cyanea, 112 records, 12 months confirmed, SST floor 20.6 °C. Barolin Point Dive Site benefits from subtropical Queensland's mild winters. O. cyanea is a warm-water specialist and the SST floor here stays comfortably within its active range year-round. GBIF records show no month with fewer than six observations, though the citizen-science bias flag applies: Bundaberg's proximity to the Coral Coast diving corridor inflates record density relative to genuinely remote Queensland reefs.

The remaining three sites — one in the Canary Islands (O. vulgaris, 67 records, 10 months), one in the Azores (O. vulgaris, 44 records, 10 months), and one in the Maldives (O. cyanea, 89 records, 11 months) — each qualify on the threshold but carry thinner records. The Canary Islands site has a strong case: SST floor of 18 °C year-round due to the Canary Current, and a well-documented O. vulgaris population. The Azores site is the most uncertain; 44 records across a decade is the minimum, and two months have single observations each.

Caveat: Three of these nine sites sit at or near the 30-record minimum. A single prolific iNaturalist contributor accounts for 11–18 records at two of them (Azores, Canary Islands). We cannot rule out that removing that contributor would drop those sites below threshold. Treat the marginal qualifiers — Krk, Azores, Canary Islands — as "likely year-round with caveats" rather than "confirmed year-round."

📅 The months that lie: reading the gaps honestly

Dive into the vibrant Adriatic Sea with this dynamic splash scene from Pula, Croatia.
Winter diving conditions Mediterranean. Photo: Francesco Sommacal / Pexels.
  • Most common gap month across all nine sites: February (7 of 9 sites show lowest monthly count in Feb)
  • Sites with a month at exactly 1 record: 4 (Krk January, Azores February, Azores December, Canary Islands January)
  • Sites with zero gap months: 3 (Red Sea, Guadeloupe, Queensland)
  • Galápagos anomaly: December–February records are 40% lower than June–August despite warmer SST

A site passing the ≥10-month threshold can still have months that are, statistically, a single lucky sighting. Krk's January record — one observation, 2021 — is not evidence of reliable January encounters. It is evidence that one diver, on one day, found one octopus. The distinction matters if you are booking a January trip specifically to see cephalopods.

The Galápagos pattern is the most ecologically interesting anomaly. Warmer water in the December–May season should, by O. bimaculoides thermal logic, produce more activity. Instead, records drop. The most plausible explanation is that Humboldt-driven upwelling in the garúa season increases prey availability — crustaceans, small fish — which draws octopus into shallower, more observable habitat. When upwelling weakens, animals may be present but foraging at depth or in less accessible terrain.[5]

Caveat: Absence of records is not absence of octopus. At every site, the gap months may reflect absent divers with iNaturalist accounts rather than absent animals. We cannot separate these signals with current data. The honest read is: "records confirm presence in these months; silence confirms nothing."

⚠️ What this list deliberately doesn't tell you

  • Encounter rate ≠ record density. Two of the nine sites have records dominated by a small number of highly active contributors. A site with 180 records from 12 divers may offer worse typical encounters than a site with 60 records from 60 independent observers. We report raw counts; we cannot normalise for contributor concentration without full GBIF contributor metadata.
  • Species identity in citizen science is imperfect. O. vulgaris and O. macropus are routinely confused in Mediterranean iNaturalist submissions. GBIF genus-level records are more reliable than species-level claims at any of these sites. Where we cite species, we are citing the dominant research-grade identification — not a guaranteed accurate ID for every record in the dataset.
  • "Year-round" is a historical description, not a forecast. The 2015–2024 window captures one full El Niño cycle and several marine heatwave events. SST anomalies in 2023–2024 shifted octopus distributions at multiple Indo-Pacific sites in ways the climatological average does not capture. A site with strong historical records may be experiencing disruption right now that won't appear in GBIF for another 12–18 months.[9]

If you've dived any of these nine sites and your experience contradicts what the occurrence record shows — better February encounters than we're projecting, or a species we've misidentified — we want to know. Corrections, additional operator contacts, and data disputes go to [email protected]. The methodology is reproducible; the dataset is not closed.