Spearfishing conditions Portugal come down to three readings of the same water: swell that stirs the bottom and kills visibility, upwelling that drops the temperature and often clears the water, and current that decides whether you should be in at all. As a rough rule, small clean swell from an offshore wind gives you clarity, while any big or messy sea churns sand and cuts what you can see. The scale you're watching is real: in a January 2026 depression, IPMA predicted northwest waves of 4 to 5 meters increasing to 7 to 8, with a possible maximum of 14 meters (IPMA, January 2026). You cannot spear in that. Below is what actually moves visibility here, and the legal kit you carry before you get wet.
- Watch swell height and period — small, long-period swell settles; short, steep swell stirs sand.
- Read the nortada and upwelling — north wind cools the water and often clears it, but pushes surface water offshore.
- Know your structure — reefs and points hold visibility differently than open beach breaks.
- Carry a legal signaling buoy — 8-liter minimum, red/orange/yellow, with an Alpha flag.
- Respect the agueiro — rip currents are the named hazard; float, don't fight.
How does swell affect underwater visibility?
Swell moves sand. The bigger and steeper it is, the more it lifts off the bottom and holds it in the water column, which is what you actually mean when you say visibility is bad. A long-period groundswell that arrives clean does less of this than a short, choppy windsea of the same height, because the energy is spread out.
IPMA publishes the numbers you need to judge this daily: minimum and maximum swell wave height in meters, predominant wave direction, and significant sea-wave height, broken down by coastal reference point through its public API (api.ipma.pt). I read swell height and period together. A meter of long swell can be diveable on a sheltered reef; a meter of short windsea over sand usually is not.
On PeelWatch the typed structure matters here — we log 4 reefs and 4 points separately from 100 beach breaks, because they hold clarity differently after a swell.
Why is the water cold and often clear in summer?
Because of upwelling driven by the nortada — the north wind that runs the west coast in summer. Jorge Ponte, chefe da Divisão de Meteorologia e Vigilância do IPMA, explained the phenomenon is directly linked to upwelling: under normal conditions this wind pushes warmer surface water offshore, allowing colder bottom water to rise near the coast (IPMA / Público).
That's why the north and central coast stay cold even in August — the rising deep water can run 4 to 6 degrees colder than expected, and it's most intense between May and September. Oceanographic researcher Isabel Iglesias (CIIMAR) noted that July 2023 saw a cooling and stabilization of sea-surface temperatures on the mainland coast mainly due to upwelling (CIIMAR).
For a spearo this cuts both ways. Upwelling often brings clearer, colder bottom water, but the same north wind that drives it also builds windsea. Cold and clear is common; you just pay for it in temperature.
What swell numbers are worth diving?
There's no single threshold that fits the whole coast, so read height, period, and direction against your spot's structure. IPMA's daily coastal marine forecast gives you the min and max swell height, predominant direction, sea-wave height, and sea-surface temperature per reference point (api.ipma.pt).
| What to check | Where it comes from | Why it matters |
|---|---|---|
| Swell wave height (min/max, m) | IPMA coastal marine forecast | Bigger swell stirs more sand |
| Predominant wave direction | IPMA coastal marine forecast | Tells you which spots are sheltered |
| Sea-surface temperature (°C) | IPMA coastal marine forecast | Cold snaps signal upwelling and often clearer water |
| Storm swell 4–14 m | IPMA, January 2026 | The scale that makes the coast undiveable |
I treat direction as the deciding factor. A swell aimed straight at your entry is a different day than the same height wrapping past a headland into shelter.
What license and safety gear does the law require?
Spearfishing — pesca submarina — needs its own license category, separate from other recreational fishing. Licenses can be daily, monthly, or annual, including a type exclusively for spearfishing, governed by Decreto-Lei nº 246/2000 (republished by DL 101/2013) and Portaria nº 14/2014 (Diário da República).
The signaling buoy is mandatory, not optional. The required equipment is a round or cylindrical buoy — red, orange, or yellow — with a minimum volume of 8 liters, fitted with an Alpha flag of the international signal code, or a board of set dimensions instead (Diário da República).
If you dive from a boat, the International Code of Signals applies: the support boat must display flag "A" from sunrise to sunset, and three lights (red-white-red) from sunset to sunrise, visible at 2 nautical miles (Diário da República).
How do rip currents change where you enter?
Rip currents — agueiros — are the named hazard on Portuguese beaches, and they decide your entry and exit more than anything else. The Autoridade Marítima Nacional spokesman explained that agueiros are marine currents caused by the return of seawater, and that if caught in one you should stay calm, try to float, and not fight against it (Autoridade Marítima Nacional).
For a spearo this is useful the other way around too. A rip is a channel of moving water, often over cleaner ground, but it will carry you offshore fast. I use structure — jetties, reefs, tidal races — to read where water is moving before I get in, and I plan the exit first.
PeelWatch logs hazards on all 120 spots — rips, jetties, tidal races, lifeguard season. Where a spot hasn't been reviewed by a human, it says so and caps what it claims. That's not modesty; it's just honest about what we've actually checked.
Reading one forecast three ways
A flat, glassy day that a surfer writes off is often the day you want. Same water, different reading. Tiago Rocha built the model to score swimming on a separate calmness scale precisely because calm and surf are opposite things — and a calm, low-swell window with an offshore wind is usually your best shot at visibility.
Start with IPMA's numbers for the raw sea state, then cross-check the specific spot's structure and hazards. Check the swim board and the tide readout on PeelWatch to find the calm, low-swell windows on your stretch — then judge visibility from there.