Onna · Japan

5.3

wave 0.4 m head-on

visibility4m

Today — right on the edge — wave, wind and visibility.

Sources: Open-Meteo · Copernicus — high confidence · data 22:37

Sources & confidence

Sources: Open-Meteo · Copernicus
Method: spearo sea-state engine: consensus of up to 6 models + satellite clarity (ZSD) + buoy-bias checks
Freshness: Re-read every hour, per coast

Compiled by the spearo sea-state engine · How it works →

The verdict comes from seven water factors and hard safety gates — not ten tabs. Go or stay.

How we score the water

Our own model

Our own forecast engine — not a third-party widget. It weighs these water factors into one go-or-stay verdict for this coast; the 0–10 dial is that verdict, read out as a number.

Swell & wave memory: Height, period and direction of the swell, plus the wake of recent storms — an old storm still stirs the water, and the engine remembers.
Wind & gusts: Speed and gusts, hour by hour — wind speed and an onshore push chop the surface and cut visibility.
Tide phase: Timing and range of the tide, calibrated per coast — big spring tides pull the verdict toward caution.
Water temperature: Sea-surface temperature — sharply cold water vetoes a green verdict.
Currents & outflow: Direction and drift of the current — it pushes you, and it drags turbid coastal water across where you dive.
Rain runoff & air clarity: Rain muddies the water inshore through land runoff, while fog and haze cut visibility at the surface.
Coast shape & exposure: How the coast faces the swell — a sheltered cove keeps the water clean; an exposed, head-on point takes a penalty.

Safety gates

Thunderstorm forecast — an instant red, no exceptions.
An official warning (MeteoAlarm / IPMA) — yellow, or red for the higher ranks.
Missing input data — a would-be green is capped to yellow rather than overstated.
Strong disagreement between forecast models — a green day is pulled back to yellow.
Night hours — where night spearfishing is banned by law the window is forced red; where it is legal (Australia outside NSW, New Zealand, South Africa) it is capped at yellow, never green.

It all folds into a single 0–10 score and one verdict: go or stay.

A forecast, not a guarantee — the sea has the last word.

Where to get in, where to hunt

Entry points with coordinates

Seabed relief — promising ground

This verdict — in your pocket. Open the app for the week's window.

Google Play — QR code — point your camera

0 m

Surface

Wind, wave and the swell windows — when to go and the best hours.

spearo.app

updated 22:37

Onna — solo, off the rocks

BORDERLINE

caution — solo off the rocks is risky, check on site · calm conditions: swell, wind and visibility all normal

wave 0.4 m head-onwind 10 km/hvisibility ~4 mwindow 06:00–21:00

today, best window 15:00–18:00

fish · Visibility 4 m · Water 28.6°C

confidence low · verdict for the selected day

Whole week — tap a day. is driving swell right now.

Solo risk: carry a float · tell someone your plan and exit time · doubt = don't go. A model-based planner; the call is made on site.

Selected day

Windows, hours
and the day's trends.

The day is picked above, in the hero. Here are that day's windows, the hour-by-hour map and the trends. Tap a window to break down the conditions.

Tuesday · today2026-10-13

06:26–18:02 · waxing crescent

▼ 02:00▲ 08:00▼ 14:00▲ 20:00mid-range tides · 1.8 m

Hours (06→20)

Day's trends

Tide0.91 m

Wave0.42 m

Wind8 km/h

Water28 °C

fish activity: moon underfoot 01:40 · high · moonrise 08:41 · moderate · moon overhead 14:00 · high · moonset 19:26 · moderate

Conditions window06:00–09:00

caution — solo off the rocks is risky, check on site fish

Hs 0.52 m · slightperiod 5.3 swind 9→18surge 0.9viz 5 m

0.52 mslight · up to ~1.04 · 316° at an angle

5.3 sswell moderate

9→18gusts 18 km/h

0.9weak surge

0.08m/s

5 mrecent swell

28.3°C5 mm + hood

▲08:00tide turn near

Atmosphere6 kmovercast

moderatemoonrise

calm conditions: swell, wind and visibility all normal
forecast models disagree (on wave, period) — lower confidence in this window
near high water — movement slowing

confidence lowtwilight

Open the seafloor map with entry points

More spots

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Nearby towns

Miyako & Yaeyama (Sakishima)

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Where to get in
off the rocks.

Scouted entries, coloured by today. The colour is the sea state at the spot, not a guarantee: the wash and a slippery entry you judge on site.

Open the seafloor map

Cape Maeda / Blue CaveOnna

borderline

Speargun prohibited, hand spear (yasu) allowed under Okinawa Fisheries Adjustment Rules art. 37. Hand-held only, no trigger or launch device. No scuba; co-op shellfish and lobster are off-limits.

exposed head-on to the swell today

window: —

Steps down the breakwater lead into the cove; the Blue Cave sits under the cliff at about 5–7 m and the reef drops off beyond to around 30 m. Very busy with tours, entry is closed in bad weather, and the cave should not be swum alone. Hand spear only — no speargun, no scuba.

Google Maps

Cape ZanpaOnna

borderline

Speargun prohibited, hand spear (yasu) allowed under Okinawa Fisheries Adjustment Rules art. 37. Hand-held only, no trigger or launch device. No scuba; co-op shellfish and lobster are off-limits.

exposed head-on to the swell today

window: —

Exposed cape in Yomitan with steep walls and drop-offs reaching 24–40 m, dived from boats; best for experienced divers. Hand spear only — no speargun, no scuba.

Google Maps

Kin Red BeachOnna

borderline

Speargun prohibited, hand spear (yasu) allowed under Okinawa Fisheries Adjustment Rules art. 37. Hand-held only, no trigger or launch device. No scuba; co-op shellfish and lobster are off-limits.

exposed head-on to the swell today

window: —

East-coast beach in Kin sheltered from northerly winds, with a shallow sandy-muddy bottom; visibility is often low. Hand spear only — no speargun, no scuba.

Google Maps

ManzamoOnna

borderline

Speargun prohibited, hand spear (yasu) allowed under Okinawa Fisheries Adjustment Rules art. 37. Hand-held only, no trigger or launch device. No scuba; co-op shellfish and lobster are off-limits.

exposed head-on to the swell today

window: —

Reef shelf below the Manzamo cliffs dived from boats; the Dream Hole is a vertical shaft from about 5 m down to 30 m. Hand spear only — no speargun, no scuba.

Google Maps

Mizugama (Kadena)Onna

borderline

Speargun prohibited, hand spear (yasu) allowed under Okinawa Fisheries Adjustment Rules art. 37. Hand-held only, no trigger or launch device. No scuba; co-op shellfish and lobster are off-limits.

exposed head-on to the swell today

window: —

Shore entry by steps on the Kadena seawall onto a calm sandy bottom with soft coral at around 10 m, dropping off to about 20–30 m with a small cave. Stays diveable in north winds; current sometimes. Hand spear only — no speargun, no scuba.

Google Maps

Sunabe SeawallOnna

borderline

Speargun prohibited, hand spear (yasu) allowed under Okinawa Fisheries Adjustment Rules art. 37. Hand-held only, no trigger or launch device. No scuba; co-op shellfish and lobster are off-limits.

exposed head-on to the swell today

window: —

Steps in the Chatan seawall lead straight onto a wide reef flat covered in soft coral that slopes to about 20–25 m. Usually little current; used heavily for training dives. Hand spear only — no speargun, no scuba.

Google Maps

Sunabe Water Treatment Plant (South Steps)Onna

borderline

Speargun prohibited, hand spear (yasu) allowed under Okinawa Fisheries Adjustment Rules art. 37. Hand-held only, no trigger or launch device. No scuba; co-op shellfish and lobster are off-limits.

exposed head-on to the swell today

window: —

Beach entry from the steps in front of the Chatan water plant; soft coral gardens lead to an intake/outlet structure at about 10–13 m that acts as a fish reef. Hand spear only — no speargun, no scuba.

Google Maps

Toilet BowlOnna

borderline

Speargun prohibited, hand spear (yasu) allowed under Okinawa Fisheries Adjustment Rules art. 37. Hand-held only, no trigger or launch device. No scuba; co-op shellfish and lobster are off-limits.

exposed head-on to the swell today

window: —

Horseshoe-shaped limestone bowl near Manza where the reef drops from about 4 m to beyond 40 m. Surge and circular currents make it a site for experienced divers. Hand spear only — no speargun, no scuba.

Google Maps

SOLO is the biggest risk: underwater you can black out from lack of oxygen silently and fatally, with no one around. Solo is never truly «safe». Below are the best weather windows; carry a buoy, tell someone your plan and exit time, and any doubt — don't go.

What's in season,
what the law says.

In season now

no targets this month

Law

Japan: spearguns and scuba/hookah are banned for all recreational fishers nationwide (Fisheries Agency prefectural gear table); a hand spear (yasu) is allowed only in some prefectures (e.g. Okinawa, Kagoshima, Nagasaki, Kochi, Mie); abalone, lobster, octopus and sea urchin in fishery-right areas belong to the local co-op, and marine park zones are closed. Check current rules locally.

Safety protocol

Sets: watch the wave trains ≥15 min before entering; Hmax ≈ 2×Hs, the wash can run 50 m past the foam line. A lull >10 min with period >12 s = a big set «overdue», do NOT enter; enter right after a full set passes and re-check at minute 30.
Exit FIRST: find your exit AND a backup before entering. On a rocky/boulder shore a 0.5 m rise in swell can make the exit impossible — getting pinned/unable to climb out is the main killer.
Headland rip: prominent points often have a permanent topographic rip regardless of the model — locate it, enter/exit on the windward side, never swim against it.
Cold: wetsuit per the SST chip; the first shiver = a metabolic surge and a drop in breath-hold → get out at the first steady shiver. Cap the session at 45–60 min below 15 °C.
Solo discipline: buoy up; tell someone the spot and exit time; conservative breath-hold (never push it in cold/murky/surfy water); visibility <3 m — don't enter.
Afternoon wind: on many coasts the wind builds from midday — plan to be out of the water by midday; the chop builds — get out.
UV 11:00–15:00 (UVI ≥6): sunscreen and cover up on the surface interval.
Solo is a fundamental risk (hypoxic blackout with no buddy). Any doubt = No-go.

FAQ — spearfishing in Onna

Where can I spearfish in Onna?

Onna has rock entry points such as Cape Maeda / Blue Cave, Manzamo and Toilet Bowl. Okinawa's west-coast resort strip from Cape Maeda (the Blue Cave) to Manzamo's cliffs — limestone walls drop straight into clear water a few fins from shore. Below you'll find each spot (access, shelter and hazards) and today's forecast.

When is the best season in Onna?

April–November; July–October is typhoon season, and the winter northerly monsoon roughs up the sea.

How cold is the water in Onna?

21–22 °C in February, 29–30 °C in August — 3–5 mm in winter, 1.5 mm in summer.

Is Onna good for a beginner?

Coral reefs and drop-offs, currents in the channels. Spearguns and scuba are banned nationwide — only a hand spear (yasu), where the prefecture allows it; shellfish, lobster, octopus and urchin in fishery-right areas belong to the co-op.

Do I need a licence in Onna?

Onna: Japan: spearguns and scuba/hookah are banned for all recreational fishers nationwide (Fisheries Agency prefectural gear table); a hand spear (yasu) is allowed only in some prefectures (e.g. Okinawa, Kagoshima, Nagasaki, Kochi, Mie); abalone, lobster, octopus and sea urchin in fishery-right areas belong to the local co-op, and marine park zones are closed. Check current rules locally.

Surface

Windows, hours
and the day's trends.

Spots in Japan

🇯🇵Japan

Nearby towns

Miyako & Yaeyama (Sakishima)

Amami & Yakushima

Kyushu & Goto

Shikoku, Kii & Ise-Shima

Help us make it better

The water column

A marine instrument,
go / no-go for solo hunting.

The seabed

The forecast is the plan.
The call is on the rock.

Where to get in
off the rocks.

Surfacing

What's in season,
what the law says.

FAQ — spearfishing in Onna

Izu Peninsula

Sagami Bay & Boso

Sea of Japan — Sado & Noto

Hokkaido

Onna spearfishing forecast — wind, swell, visibility, tides & live cameras

Windows, hours and the day's trends.

Get the go / no-go verdict for Onna by email

Spots in Japan

🇯🇵Japan

Nearby towns

Miyako & Yaeyama (Sakishima)

Amami & Yakushima

Kyushu & Goto

Shikoku, Kii & Ise-Shima

Help us make it better

A marine instrument, go / no-go for solo hunting.

The forecast is the plan.The call is on the rock.

Where to get in off the rocks.

What's in season, what the law says.

FAQ — spearfishing in Onna

Izu Peninsula

Sagami Bay & Boso

Sea of Japan — Sado & Noto

Hokkaido

Windows, hours
and the day's trends.

A marine instrument,
go / no-go for solo hunting.

The forecast is the plan.
The call is on the rock.

Where to get in
off the rocks.

What's in season,
what the law says.