Today — sit it out — wave, wind and surge pounding. 💧 Water should clear by Friday (~3d)
Sources & confidence
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.
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.
Safety gates
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
Leave your email — and the moment a window opens at Katsuura, we'll send the go / no-go verdict. Email is all we need.
What's missing? Tell us what you'd like to see — new spots, species, data or features. We read everything.
Wind, wave and the swell windows — when to go and the best hours.
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.
Visibility and what drives it — post-storm clearing, river plume, temperature and the thermocline.
spearo.app folds wind, wave, swell period, visibility, tides, water temperature and risk into a single verdict — go to the spot or not. It computes 7 days ahead from open marine models (Open-Meteo, IPMA), with no sign-up and no accounts. Built for solo spearfishing off the rocks, where any mistake costs dearly.
Now live: 3016 spots across 406 stretches of coast — mainland Portugal, Madeira and the Azores.
See all spotsRelief and bottom type, tides, and the depths of each spot.
The models set the window. Whether you go in is read only at the water: count the sets, watch the surge on the entry. If in doubt, you don't get in.
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 mapShore dive beside the Katsuura underwater observation tower: an enclosed former lobster pen (1.5–2.5 m) and shallows (1–3.5 m) lead to east and west rock reefs at 3.5–14 m and a sandy bowl at 8–14 m. The outer reef (5–12 m) gets current and poorer visibility at times. Marine-park area, entry via the local dive services. Marine park zone — take nothing.
Google MapsReef, rocky reef, 2–12 m, from shore. Spearing not permitted in Chiba — check local rules. Coords approx.
Cameras, map and reference — to hand as you come up.
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.
Ubara Island east side, 3 minutes by boat from the harbour: reef top at 5 m, walls, ledges and boulders to about 18 m and wide sand around 25 m. Suitable for all levels. Spearing not permitted in Chiba — check local rules.
Google MapsSOLO 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.
Katsuura has rock entry points such as Katsuura marine park (Yoshio), Okitsu and Ubara. Boso's Pacific coast — fishing port, the Katsuura marine park with its underwater observation tower at Yoshio, rocky reefs at Okitsu and Ubara. Below you'll find each spot (access, shelter and hazards) and today's forecast.
June–November; the Kuroshio keeps the water warm into late autumn, winter brings the north-west monsoon, and typhoons come August–October.
14–17 °C in February–March, 26–28 °C in August — 5–7 mm in winter, 3 mm in summer.
Rocky capes and reefs, Pacific swell and currents off the points. 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.
Katsuura: 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.
