Trearddur Bay
Good to go
No current pollution alerts — always assess conditions yourself.
Checked against Natural Resources Wales · data last changed 2 months ago.
Sea conditions
Water temperature
15.2°C
Cool — comfortable for a shorter swim
Wave height
0.8 m
Significant wave height offshore; inshore conditions vary.
Tide
Coming in
- High water around UTC
- Low water around UTC
Modelled values, not measurements — coastal water often differs from the open-sea model, and tide times are approximate to within about half an hour. Use official tide tables for anything that depends on precise timing.
This spot’s record
Trearddur Bay is in Isle of Anglesey, about 4 km from Holyhead. Trearddur Bay was rated Good in 2025 by Natural Resources Wales. Its previous classifications were Good in 2024, Excellent in 2023 and Excellent in 2022, so the rating here has moved rather than held. Across the 12 most recent samples published by Natural Resources Wales, E. coli counts ranged from 10 to 18 per 100 ml. The highest was taken on 2 September 2026. A classification is calculated from percentiles across four seasons, so no single reading decides how this water is rated.
Recent sample results
The last 12 bacterial samples published by Natural Resources Wales, most recent on the right. Counts are per 100 ml of water.
Dashed line: 500 E. coli per 100 ml, the Bathing Water Directive guide value for coastal / transitional waters.
| Date | E. coli | Enterococci | Assessment |
|---|---|---|---|
| 16 Sept | 10 | 10 | — |
| 2 Sept | 18 | 10 | — |
| 17 Aug | 10 | 10 | — |
| 3 Aug | 10 | 10 | — |
| 21 Jul | 10 | 10 | — |
| 6 Jul | 10 | 10 | — |
A bathing water's official classification is calculated from percentiles across four bathing seasons, not from any single sample — so one high reading doesn't mean a spot is unsafe, and one low reading doesn't mean it's clean today.
Quality over the last 4 years
- Excellent2022
- Excellent2023
- Good2024
- Good2025
This water has declined, from Excellent in 2022 to Good in 2025.
Facilities & access
- Parking
- YesCar park about 150 m away (OpenStreetMap)
- Toilets
- YesPublic toilets about 150 m away (OpenStreetMap)
Official water quality
Classified Good in 2025.
Official bathing-water profileCommon questions
- Can you swim at Trearddur Bay right now?
- Trearddur Bay is currently marked "Good to go". No current pollution alerts — always assess conditions yourself. This reflects the latest data published by Natural Resources Wales. Conditions change quickly — always assess the water yourself before entering.
- What is the water quality like at Trearddur Bay?
- Natural Resources Wales classified Trearddur Bay as Good in 2025. Classifications are a rolling assessment of bacterial samples taken over four bathing seasons, measured against E. coli and intestinal enterococci limits set by the EU Bathing Water Directive.
- Is there a swimming ban or warning at Trearddur Bay?
- There are no active bathing restrictions published by Natural Resources Wales for Trearddur Bay. That is not a guarantee of safety — assess conditions yourself.
- What facilities are there at Trearddur Bay?
- Trearddur Bay has toilets, parking. Facility information comes from OpenStreetMap contributors.
Get told when this changes
We’ll email you when the swim status at Trearddur Bay moves — a pollution alert opening, or one lifting. Not a newsletter: only this spot, only when it changes, at most once every 12 hours.
Your address is used for these alerts and nothing else, is never shared, and is deleted the moment you unsubscribe — a link is in every email.
Nearby swimming spots
See all swimming spots near Holyhead — about 4 km away.