Water quality indicators for swimming and diving
50 coastal spots ranked by satellite-derived water quality indicators. Chlorophyll, dissolved oxygen and nutrient data from Copernicus Marine, updated daily.
Not bathing-water safety advice. Check official local notices before entering the water.
How we score water cleanliness
An indicator average of five satellite-derived water quality signals, normalised to a 0 to 100 scale. Lower is better.
Lower score means better modelled clarity and quality indicators. It cannot rule out short-lived pollution, bacteria, algal toxins or local runoff.
| # | Location | Country | Score ↑ | Rating | Chlorophyll | Dissolved O₂ | Nitrate | Phosphate | SPM |
|---|---|---|---|---|---|---|---|---|---|
| 1 | El Quemao | Spain | 2 | Pristine | 0.2 mg/m3 | - ml/L | - mmol/m3 | - mmol/m3 | 0.3 g/m3 |
| 2 | Praia do Amado | Portugal | 4 | Pristine | 0.3 mg/m3 | 5.48 ml/L | 0.04 mmol/m3 | 0.008 mmol/m3 | 0.4 g/m3 |
| 3 | Margaret River | Australia | 4 | Pristine | 0.4 mg/m3 | - ml/L | - mmol/m3 | - mmol/m3 | 1.2 g/m3 |
| 4 | Nazaré | Portugal | 5 | Pristine | 0.4 mg/m3 | 5.71 ml/L | 0.57 mmol/m3 | 0.001 mmol/m3 | 1.7 g/m3 |
| 5 | La Santa | Spain | 6 | Pristine | 0.2 mg/m3 | 4.99 ml/L | 0.00 mmol/m3 | 0.072 mmol/m3 | 0.3 g/m3 |
| 6 | Gracetown | Australia | 6 | Pristine | 0.2 mg/m3 | 5.17 ml/L | 0.01 mmol/m3 | 0.124 mmol/m3 | 0.6 g/m3 |
| 7 | Seaburn | United Kingdom | 6 | Pristine | 0.9 mg/m3 | 5.95 ml/L | 1.20 mmol/m3 | 0.225 mmol/m3 | 0.7 g/m3 |
| 8 | Oludeniz | Turkey | 7 | Pristine | 0.1 mg/m3 | 4.71 ml/L | 0.18 mmol/m3 | 0.000 mmol/m3 | 0.3 g/m3 |
| 9 | Lakey Peak | Indonesia | 7 | Pristine | 0.8 mg/m3 | - ml/L | - mmol/m3 | - mmol/m3 | 0.5 g/m3 |
| 10 | Fraserburgh | United Kingdom | 7 | Pristine | 1.1 mg/m3 | 6.15 ml/L | 2.76 mmol/m3 | 0.016 mmol/m3 | 1.0 g/m3 |
| 11 | Saint-Leu | Réunion | 8 | Pristine | 0.1 mg/m3 | 4.71 ml/L | 0.00 mmol/m3 | 0.141 mmol/m3 | 0.2 g/m3 |
| 12 | Ponta Preta | Cape Verde | 8 | Pristine | 0.3 mg/m3 | 4.78 ml/L | 0.01 mmol/m3 | 0.085 mmol/m3 | 0.2 g/m3 |
| 13 | Vliho Bay | Greece | 8 | Pristine | 0.3 mg/m3 | 4.71 ml/L | 0.41 mmol/m3 | 0.000 mmol/m3 | 0.3 g/m3 |
| 14 | Bundoran | Ireland | 8 | Pristine | 0.6 mg/m3 | - ml/L | - mmol/m3 | - mmol/m3 | 2.3 g/m3 |
| 15 | Huanchaco | Peru | 8 | Pristine | 0.9 mg/m3 | - ml/L | - mmol/m3 | - mmol/m3 | 0.8 g/m3 |
| 16 | Imsouane | Morocco | 8 | Pristine | 1.1 mg/m3 | 5.46 ml/L | 0.12 mmol/m3 | 0.084 mmol/m3 | 0.8 g/m3 |
| 17 | Arugam Bay | Sri Lanka | 9 | Pristine | 0.1 mg/m3 | 4.53 ml/L | 0.02 mmol/m3 | 0.102 mmol/m3 | 0.3 g/m3 |
| 18 | Playa Grande | Costa Rica | 9 | Pristine | 0.2 mg/m3 | 4.82 ml/L | 0.08 mmol/m3 | 0.316 mmol/m3 | 0.3 g/m3 |
| 19 | Muizenberg | South Africa | 9 | Pristine | 1.6 mg/m3 | 5.92 ml/L | 0.72 mmol/m3 | 0.275 mmol/m3 | 0.3 g/m3 |
| 20 | Barra de la Cruz | Mexico | 10 | Pristine | 0.1 mg/m3 | 4.61 ml/L | 0.04 mmol/m3 | 0.327 mmol/m3 | 0.3 g/m3 |
| 21 | Cimaja | Indonesia | 10 | Pristine | 0.4 mg/m3 | 4.68 ml/L | 0.37 mmol/m3 | 0.206 mmol/m3 | 0.7 g/m3 |
| 22 | Nihiwatu | Indonesia | 10 | Pristine | 0.7 mg/m3 | 4.65 ml/L | 0.01 mmol/m3 | 0.109 mmol/m3 | 0.3 g/m3 |
| 23 | El Palmar | Spain | 10 | Pristine | 1.2 mg/m3 | 5.02 ml/L | 0.02 mmol/m3 | 0.035 mmol/m3 | 0.6 g/m3 |
| 24 | Scarborough | United Kingdom | 10 | Pristine | 1.3 mg/m3 | 6.06 ml/L | 0.89 mmol/m3 | 0.328 mmol/m3 | 3.7 g/m3 |
| 25 | Dungeons | South Africa | 10 | Pristine | 1.5 mg/m3 | 5.73 ml/L | 1.10 mmol/m3 | 0.287 mmol/m3 | 0.5 g/m3 |
| 26 | Kimmeridge Bay | United Kingdom | 10 | Pristine | 1.6 mg/m3 | 5.62 ml/L | 0.90 mmol/m3 | 0.004 mmol/m3 | 2.5 g/m3 |
| 27 | San José del Cabo | Mexico | 11 | Pristine | 0.3 mg/m3 | 4.68 ml/L | 0.01 mmol/m3 | 0.529 mmol/m3 | 0.4 g/m3 |
| 28 | Huntington Beach | United States | 11 | Pristine | 1.5 mg/m3 | 5.84 ml/L | 0.33 mmol/m3 | 0.563 mmol/m3 | 0.7 g/m3 |
| 29 | Bournemouth | United Kingdom | 11 | Pristine | 1.9 mg/m3 | 5.59 ml/L | 0.76 mmol/m3 | 0.002 mmol/m3 | 3.1 g/m3 |
| 30 | El Sunzal | El Salvador | 12 | Pristine | 0.2 mg/m3 | 4.72 ml/L | 1.13 mmol/m3 | 0.498 mmol/m3 | 0.3 g/m3 |
| 31 | Puerto Escondido | Mexico | 12 | Pristine | 0.2 mg/m3 | 4.63 ml/L | 0.02 mmol/m3 | 0.322 mmol/m3 | 3.8 g/m3 |
| 32 | Troncones | Mexico | 12 | Pristine | 0.4 mg/m3 | 5.01 ml/L | 0.32 mmol/m3 | 0.239 mmol/m3 | 5.6 g/m3 |
| 33 | Newgale | United Kingdom | 12 | Pristine | 2.2 mg/m3 | 5.57 ml/L | 1.39 mmol/m3 | 0.000 mmol/m3 | 1.7 g/m3 |
| 34 | Cloudbreak | Fiji | 13 | Pristine | 0.5 mg/m3 | 4.61 ml/L | 0.00 mmol/m3 | 0.171 mmol/m3 | 4.6 g/m3 |
| 35 | Jeffreys Bay | South Africa | 13 | Pristine | 2.0 mg/m3 | 5.13 ml/L | 0.36 mmol/m3 | 0.187 mmol/m3 | 0.4 g/m3 |
| 36 | Bloubergstrand | South Africa | 13 | Pristine | 2.4 mg/m3 | 5.79 ml/L | 0.80 mmol/m3 | 0.341 mmol/m3 | 0.8 g/m3 |
| 37 | Cocoa Beach | United States | 16 | Clean | 0.8 mg/m3 | 4.52 ml/L | 0.09 mmol/m3 | 0.000 mmol/m3 | 7.8 g/m3 |
| 38 | Saunton Sands | United Kingdom | 16 | Clean | 2.1 mg/m3 | 5.96 ml/L | 5.93 mmol/m3 | 0.021 mmol/m3 | 3.2 g/m3 |
| 39 | Woolacombe | United Kingdom | 16 | Clean | 2.1 mg/m3 | 5.96 ml/L | 5.93 mmol/m3 | 0.021 mmol/m3 | 3.2 g/m3 |
| 40 | Cannon Beach | United States | 17 | Clean | 3.3 mg/m3 | 6.36 ml/L | 2.40 mmol/m3 | 0.305 mmol/m3 | 1.8 g/m3 |
| 41 | Torres | Brazil | 18 | Clean | 4.1 mg/m3 | 5.68 ml/L | 0.13 mmol/m3 | 0.110 mmol/m3 | 2.0 g/m3 |
| 42 | Sopelana | Spain | 19 | Clean | 0.2 mg/m3 | 5.14 ml/L | 13.86 mmol/m3 | 0.001 mmol/m3 | 0.3 g/m3 |
| 43 | Guéthary | France | 19 | Clean | 0.4 mg/m3 | 5.18 ml/L | 12.78 mmol/m3 | 0.001 mmol/m3 | 1.0 g/m3 |
| 44 | Mundaka | Spain | 20 | Clean | 0.3 mg/m3 | 5.09 ml/L | 14.57 mmol/m3 | 0.000 mmol/m3 | 0.3 g/m3 |
| 45 | Varkala | India | 20 | Clean | 2.8 mg/m3 | 4.62 ml/L | 0.69 mmol/m3 | 0.257 mmol/m3 | 2.0 g/m3 |
| 46 | Hiriketiya | Sri Lanka | 20 | Clean | 3.2 mg/m3 | 4.67 ml/L | 0.73 mmol/m3 | 0.259 mmol/m3 | 0.4 g/m3 |
| 47 | Caswell Bay | United Kingdom | 26 | Clean | 3.7 mg/m3 | 5.96 ml/L | 5.93 mmol/m3 | 0.021 mmol/m3 | 10.0 g/m3 |
| 48 | Raglan | New Zealand | 31 | Moderate | 2.3 mg/m3 | - ml/L | - mmol/m3 | - mmol/m3 | 8.7 g/m3 |
| 49 | Ocean Beach SF | United States | 31 | Moderate | 4.6 mg/m3 | 6.10 ml/L | 0.99 mmol/m3 | 0.657 mmol/m3 | 14.4 g/m3 |
| 50 | Lobitos | Peru | 38 | Moderate | 2.6 mg/m3 | 4.15 ml/L | 8.86 mmol/m3 | 1.088 mmol/m3 | 5.7 g/m3 |
Satellite data from Copernicus Marine. Data from 8 July 2026
Frequently asked questions
How is the cleanliness score calculated?
We compute an indicator average of five satellite-derived water quality signals: Chlorophyll-a (35%), dissolved oxygen (30%), nitrate (15%), phosphate (10%) and SPM (10%). Each raw value is normalised to a 0 to 100 sub-index, then weighted. Lower is better for modelled clarity and quality indicators, but this is not bathing-water safety advice.
What does dissolved oxygen indicate?
Dissolved oxygen (ml/L) measures how much oxygen is available in the water. Healthy coastal waters typically have 5 to 8 ml/L. Low levels (below 2 ml/L) indicate hypoxia or dead zones, usually caused by nutrient pollution and algal decay. For swimmers, low oxygen is a warning sign of poor water quality and ecological stress.
What are nitrate and phosphate?
Nitrate and phosphate are dissolved nutrients that enter coastal waters from agricultural runoff, sewage, and industrial discharge. Elevated levels fuel algal blooms and eutrophication. Nitrate above 10 mmol/m3 and phosphate above 1 mmol/m3 typically indicate significant nutrient pollution. The data comes from the Copernicus Marine biogeochemistry model at 0.25 degree resolution.
Why not use bacteria testing data?
Faecal indicator bacteria (E. coli, enterococci) are the gold standard for bathing-water health, but they can only be measured from in-water sampling, not from satellites. National agencies like the Environment Agency (England) and EEA (Europe) run sampling programmes, but coverage is limited to specific regions. We show this data as a supplementary badge where available, but the global score uses satellite-derived indicators for consistent, worldwide comparison. Check official local notices before entering the water.
What does chlorophyll indicate?
Chlorophyll-a concentration (mg/m3) is a proxy for phytoplankton density. Low values typically mean clear, nutrient-poor water. Elevated levels above 5 mg/m3 may indicate an algal bloom, which can reduce visibility and occasionally cause irritation.
What is SPM / turbidity?
Suspended Particulate Matter (g/m3) measures particles floating in the water column (sediment, runoff, organic matter). Higher values mean murkier water and often indicate recent storm activity, river runoff, or pollution discharge.
Where does the data come from?
Two Copernicus Marine products. Ocean colour observations (4km resolution) provide chlorophyll-a and SPM from merged satellite data. The biogeochemistry model (0.25 degree resolution) provides dissolved oxygen, nitrate, and phosphate from the GLOBAL_ANALYSISFORECAST_BGC_001_028 product, updated daily.
How often is the data updated?
The data pipeline runs daily at 10:00 UTC. Ocean colour data typically lags by 1 to 2 days. The biogeochemistry model provides analysis and short-range forecast data, usually available within 24 hours.
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