Cemaes Bay tides today
- Tide now 16.7 ft ↑ rising · high 11:37 pm (19.2 ft)
- Best time tomorrow 6:00–7:00 pm good day · 7/10
- Beach day Not today Not a beach day · 0/10
- Waves · water 2.6 ft · 56 °F slight · 5.4 s from the southwest
- Wind · air 9 mph · 55 °F from the SSW, gusts 14 · overcast
- Sun 7:09 am–4:53 pm 9 h 44 min of daylight
- Moon 92% · 5:30 pm waning gibbous · rises at 5:30 pm
- Diving tomorrow 10:40 am–1:00 pm good day · 8/10
Today in Cemaes Bay there are high tides at 11:12 am (19.2 ft) and 11:37 pm (19.2 ft) and low tides at 5:00 am and 5:24 pm. Tide coefficient 92. Right now the tide is rising toward the high tide at 11:37 pm. The sun rises at 7:09 am and sets at 4:53 pm: 9 h 44 min of daylight. The moon is 92% illuminated (waning gibbous) and rises at 5:30 pm. Major solunar periods run from 12:40 am to 2:40 am and from 1:12 pm to 3:12 pm. The next spring tides arrive from October 26 to 28. The sea is slight, with 2.6 ft waves. There's a gentle breeze from the south-southwest (9 mph). Overcast, 55 °F.
Fishing in Cemaes Bay today
Best time to fish
Solunar activity today: high- Low tide at 5:24 pm
- Minor period 5:00–6:00 pm (moonrise)
- Sunset at 4:53 pm, golden hour from 4:02 pm
- Rising pressure (+0.37 inHg in 24 h), light offshore wind (9 mph) and some swell (2.9 ft waves) to stir the water
- Waning gibbous: a bit more activity than at the quarters
- Highest tide coefficient today: 92 (spring tides)
- A minor period lines up with sunset
Your day at a glance
The best window, 4:20 pm to 5:30 pm, combines the 5:24 pm low tide, moonrise, sunset and some swell, though with rising pressure. Also worth a try from 10:20 am to 11:20 am, with the 11:12 am high tide, moonset and some swell, though with rising pressure and moderate wind.
Species with the most records nearby: small-spotted catshark, European plaice, whiting and thornback ray. October is one of the months when these are seen most: European plaice and whiting. What you can catch
Beach day in Cemaes Bay
Is it a beach day?
- Calm for swimming: 4.5 ft waves
- Cloudy (82% cloud cover)
- Feels like 52 °F: chilly for the beach
- Fresh cross-shore wind (19 mph): blowing sand
- Water at 56 °F (very cold)
- High tide at 11:12 am, coefficient 92: little sand left
Today, hour by hour
- Swimming Calm · 4.5 ft
4.5 ft waves: calm for swimming. Low rip current risk. Always follow the lifeguard's flags.
- Water 56 °F
Very cold: ease in and keep swims short.
- Sun & sunscreen UV 1 · SPF 15
Max UV 1 (low): SPF 15 sunscreen.
- Wind 19 mph
Fresh cross-shore wind (19 mph): blowing sand.
- Tide & sand 5:00 am
Low tide at 5:00 am and 5:24 pm: that's when there's the most sand. High tide at 11:12 am and 11:37 pm. Coefficient 92 (spring tides): little sand left at high tide.
We don't have data on jellyfish, sargassum or beach closures: ask the lifeguard or check with the local beach authority. How it works · The next 7 days
Beaches near Cemaes Bay
Map: OpenFreeMap · © OpenMapTiles · © OpenStreetMap contributors
- Traeth Bach 0.1 mi · N
- Restrooms
- Parking
- Traeth Mawr 0.2 mi · NE
- Restrooms
- Parking
Sufficient water quality 2025 season, Natural Resources Wales
- Church Bay 5.0 mi · SW
- Restrooms
- Parking
Excellent water quality 2025 season, Natural Resources Wales
- Porth y Cychod 5.2 mi · SW
- Restrooms
- Parking
- Porth y Santes 5.2 mi · SW
- Restrooms
- Parking
- Porth y Pren 5.2 mi · SW
- Restrooms
- Parking
- Porth Tyddyn-uchaf 5.3 mi · SW
- Porth Trwyn 5.8 mi · SW
- Parking
Named beaches within 6.2 mi, nearest first. Amenities from OpenStreetMap: some may be missing or out of date. View on OpenStreetMap · Add or fix on OpenStreetMap
Beaches and amenities: © OpenStreetMap contributors (ODbL).
UK bathing water quality: Natural Resources Wales. Contains public sector information licensed under the Open Government Licence v3.0. Full attribution.
Webcams near Cemaes Bay
Webcams provided by windy.com — add a webcam
Tides in Cemaes Bay
Today's high and low tides
- ▼ Low tide 5:00 am 3.2 ft
- ▲ High tide 11:12 am 19.2 ft · coef. 92
- ▼ Low tide 5:24 pm 3.1 ft
- ▲ Next high tide 11:37 pm 19.2 ft · coef. 91
↑ Rising The tide is rising. 1 h 44 min to high tide at 11:37 pm.
Tide coefficient 92 for the 11:12 am high tide and 91 for the 11:37 pm high tide. Spring tides. The water rises and falls 16.1 ft between the highest high and the lowest low: a large range for this place. 70 is an average tide here; 90 and above means spring tides; below 45, neap tides. What is the tide coefficient?
2026 extremes: the highest tide of the year is on December 26 (20.4 ft) and the lowest, on August 14 (0.7 ft).
Semidiurnal: two high and two low tides a day, of similar height.
Heights above chart datum: the lowest astronomical tide (LAT), the zero of nautical charts in Europe. Astronomical prediction: wind and air pressure can raise or lower the water by a few inches, and more in a storm. Not for navigation. chart datum (LAT)
Tide coefficient and range in October
The biggest tides of the month came from October 26 to 28 (coefficient 93, 16.4 ft range). The smallest, from October 19 to 20 (coefficient 37, 7.2 ft).
Tide and solunar table · this week
| Day | Sun | Tide 1 | Tide 2 | Tide 3 | Tide 4 | Coef. | Moon | Major periods | Activity |
|---|---|---|---|---|---|---|---|---|---|
| Today, Wed 28 | 7:09 am · 4:53 pm | Low tide 5:00 am · 3.2 ft | High tide 11:12 am · 19.2 ft | Low tide 5:24 pm · 3.1 ft | High tide 11:37 pm · 19.2 ft | Coef. 92 | 92% | Major periods 12:40 am · 1:12 pm | High |
| Thu 29 | 7:11 am · 4:51 pm | Low tide 5:43 am · 3.6 ft | High tide 11:56 am · 19.0 ft | Low tide 6:12 pm · 3.4 ft | — | Coef. 88 | 85% | Major periods 1:44 am · 2:16 pm | Medium |
| Fri 30 | 7:13 am · 4:49 pm | High tide 12:25 am · 18.5 ft | Low tide 6:30 am · 4.3 ft | High tide 12:44 pm · 18.5 ft | Low tide 7:05 pm · 4.1 ft | Coef. 84 | 76% | Major periods 2:49 am · 3:20 pm | Medium |
| Sat 31 | 7:15 am · 4:47 pm | High tide 1:20 am · 17.6 ft | Low tide 7:22 am · 5.3 ft | High tide 1:40 pm · 17.9 ft | Low tide 8:05 pm · 4.9 ft | Coef. 75 | 65% | Major periods 3:51 am · 4:21 pm | Medium |
| Sun 1 | 7:17 am · 4:45 pm | High tide 2:23 am · 16.6 ft | Low tide 8:22 am · 6.3 ft | High tide 2:44 pm · 17.1 ft | Low tide 9:15 pm · 5.6 ft | Coef. 65 | Last quarter | Major periods 4:50 am · 5:18 pm | Medium |
| Mon 2 | 7:18 am · 4:44 pm | High tide 3:38 am · 15.7 ft | Low tide 9:33 am · 7.0 ft | High tide 4:00 pm · 16.5 ft | Low tide 10:33 pm · 5.8 ft | Coef. 56 | 43% | Major periods 5:44 am · 6:09 pm | Medium |
| Tue 3 | 7:20 am · 4:42 pm | High tide 5:03 am · 15.3 ft | Low tide 10:55 am · 7.1 ft | High tide 5:23 pm · 16.3 ft | Low tide 11:52 pm · 5.4 ft | Coef. 54 | 32% | Major periods 6:34 am · 6:57 pm | Medium |
▲ high tide · ▼ low tide · heights above chart datum (LAT). Major periods: start time; they last 2 hours. Activity: based on the moon phase and the solunar periods.
Where this tide comes from
Cemaes Bay has no station of its own, so we use the tide at Holyhead (Environment Agency), 9.7 mi away. On the open coast the difference is usually a few minutes and inches; inside estuaries, rivers and enclosed bays it can be much larger.
Station data attribution: This uses Environment Agency tide gauge data from the real-time data API (Beta): Holyhead (E70524), https://environment.data.gov.uk/flood-monitoring/id/stations/E70524. Contains public sector information licensed under the Open Government Licence v3.0 (https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/). Modified: harmonic constants fitted by TidePlanet from the 15-minute sea levels of 2025-10-29 to 2026-10-22 (356 days).
The sea at Cemaes Bay
Sea stateSea state: slight
The waves you may find
- Most commonMost common1.3 ft
- Significant2.6 ft
- Highest expectedHighest5.4 ft
One wave in seven is higher than the significant height, and about 3 times a day one reaches 5.4 ft. Before heading out, expect waves of up to 5.4 ft.
Wind on the coast and offshore
Offshore wind. The coast faces north and the wind blows from land out to sea: calm shore and clean waves, but watch the drift out to sea.
Wave height, next 7 daysWaves, next 7 days
Waves ease over the next few days. The biggest waves arrive on Wednesday 28: 5.0 ft with a period of 7 s, from the southwest (moderate).
Water temperature
Water temperature →Water temperature changes how fish behave: in very cold or very warm water they feed less. The water cools over the next few days: about 54.6 °F by Tuesday 3.
Water about normal for late October.
Satellite: NASA MUR (JPL MUR MEaSUREs, PO.DAAC), doi:10.5067/GHGMR-4FJ04. Sources and licenses
Water temperature →Forecast from Open-Meteo (CC BY 4.0) with models from ECMWF, NOAA, Météo-France, DWD, Copernicus Marine and CAMS. Updated at 9:53 pm (local time).
Surf in Cemaes Bay today
Surf today
Poor- 1.4–2.2 ft surf at the shore, a fun size for most surfers
- 2.4 ft swell at 8 s from the southwest, short: weak, messy waves; it hits this coast at an angle
- 3.6 ft wind swell at 5 s: messy waves
- Fresh cross-shore wind (19 mph): a bit of chop
- Rising tide (high tide at 11:12 am)
- Light: First light 6:33 am · sunrise 7:09 am · sunset 4:53 pm · last light 5:30 pm
- Tide: low 5:00 am (3.2 ft), high 11:12 am (19.2 ft), low 5:24 pm (3.1 ft) and high 11:37 pm (19.2 ft). Every break has its own tide: some work at low tide and others at high tide. The tide doesn’t change the score here.
- Water at 55.4 °F: a 5/4 fullsuit with booties (and a hood if it’s windy).
- Energy: 125 kJ · Medium power
Today’s surf at a glance
The best window is 7:00 am to 11:00 am, though with a short-period swell, wind swell and cross-shore wind.
An estimate for this stretch of coast, not for a specific break: every beach or reef works its own way (its tide, bottom and angle). Check it when you get there.
Follow the flags and the lifeguards, and don’t paddle out if the surf is above your level: this score is a guide, not a substitute for what you see when you get there.
Diving in Cemaes Bay today
Diving and snorkeling today
Likely visibility: fair- Slack water around high tide (11:12 am): little current from 10:40 am to 11:40 am
- 2.6 ft swell at 7 s from the southwest: some surge on the bottom
- Moderate cross-shore wind (17 mph)
- 0.6 mph current toward the east-northeast (model)
- Sun high: more light underwater
- Slack water today: low tide 5:00 am (4:40–5:20 am), high tide 11:12 am (10:40–11:40 am), low tide 5:24 pm (5:00–5:40 pm) and high tide 11:37 pm (11:10 pm–12:00 am)
- Likely visibility: fair. Swell (up to 3.1 ft at 9 s) and wind over the last few days have stirred up the water. Based on the last 24 hours of data.
- Water at 55.4 °F: a 7 mm semi-dry suit, with hood, gloves and booties.
- Snorkeling: better not, with these waves, wind or current.
- Night dive: dark from 5:30 pm. Waning gibbous (92%), rising at 5:30 pm: a bright night.
Your diving day at a glance
The best window, 10:30 am to 12:10 pm, combines slack water at high tide and the sun high, though with moderate wind and current. Also worth a look from 4:10 pm to 4:50 pm, with light wind, though with current.
Slack water comes from the tide: in inlets, channels and between islands the water can keep running for an hour or two after. Ask the local dive shop.
Never dive alone and check with the local dive shop: this rating is a guide, not a substitute for a professional.
Dive sites, wrecks and dive shops nearby
Map: OpenFreeMap · © OpenMapTiles · © OpenStreetMap contributors
- Abbotsford 1.3 mi
- President Harbitz 1.8 mi
- Liverpool 2.0 mi
- La Plata 2.9 mi
- Lightstone 3.7 mi
- Apapa 3.9 mi
- Fawn 4.1 mi
- Albert 4.2 mi
- Lilly 4.3 mi
- Minerva 4.5 mi
- Dakota 4.6 mi
- Anglesey Divers 10 mi
Within 12 mi. Some may be missing or closed; marine reserves usually need a permit. Open the map on OpenStreetMap · Missing one? Add it to OpenStreetMap
Wreck and reef positions are approximate and not for navigation; a wreck’s depth runs from the top of the hull to the seabed.
Sites: © OpenStreetMap contributors (ODbL). Wrecks: EMODnet Human Activities (AND-International), from UK Hydrographic Office data, CC BY 4.0. Contains public sector information licensed under the Open Government Licence v3.0.
Weather in Cemaes Bay
Now in Cemaes Bay
- Low / high
- 53 / 58 °F
- Rain
- 0.11 in · 100%
- Clouds
- 100%
- Humidity
- 94%
- Dew pointDew point
- 53 °F
- Visibility
- 9.0 mi
- UV indexUV
- 0 · low
- Air qualityAir
- Fair · 28
- Saharan dust
- No
- Pollen
- None
Pressure and fishing
- ↗ RisingRising · now Anglers say fish bite less for a while
- → SteadySteady Anglers expect normal activity
- ↘ FallingFalling Anglers say fish feed more before the change
Rising now (+0.03 inHg in 3 hours). Over the next 48 hours: +0.15 inHg. Rising pressure: anglers say fish bite less for a while. Fast changes, either way, tend to affect fishing.
Today, hour by hourHour by hour
Bars: mean wind. Dashed line: gusts. Arrows point where the wind blows to.
| Time | 12:00 am | 3:00 am | 6:00 am | 9:00 am | 12:00 pm | 3:00 pm | 6:00 pm | 9:00 pm |
|---|---|---|---|---|---|---|---|---|
| Sky | Partly cloudy | Light rain | Light rain | Partly cloudy | Partly cloudy | Overcast | Overcast | Overcast |
| Temperature | 53° | 55° | 56° | 56° | 57° | 57° | 55° | 55° |
| Wind (mph) | 20 SW | 21 SW | 23 SW | 18 WSW | 17 WSW | 14 WSW | 10 SSW | 9 SSW |
| Gusts | 32 | 34 | 39 | 30 | 30 | 26 | 15 | 14 |
| Waves | 4.4 ft | 4.9 ft | 5.0 ft | 4.3 ft | 3.7 ft | 3.2 ft | 2.8 ft | 2.6 ft |
| Rain | 0.00 in | 0.03 in | 0.01 in | 0.00 in | 0.00 in | 0.00 in | 0.00 in | 0.00 in |
- 9:00 pm 55° 9 SSW 2.6 ft
- 12:00 am 55° 9 SSW 2.6 ft
- 3:00 am 55° 8 SSW 2.4 ft
- 6:00 am 54° 8 S 2.2 ft
- 9:00 am 55° 9 S 2.1 ft
- 12:00 pm 57° 14 S 2.2 ft
- 3:00 pm 56° 11 S 2.2 ft
- 6:00 pm 54° 5 SSE 2.2 ft
Next 14 daysComing days
| Day | Sky | Low / high | Max wind | Max wave | High tides |
|---|---|---|---|---|---|
| Today · 28 | 53 / 58 °F | 24 mph SW | 5.0 ft | 11:12 am · 11:37 pm | |
| Thu 29 | 52 / 57 °F | 14 mph S | 2.6 ft | 11:56 am | |
| Fri 30 | 50 / 57 °F | 14 mph S | 2.7 ft | 12:25 am · 12:44 pm | |
| Sat 31 | 47 / 58 °F | 5 mph S | 1.4 ft | 1:20 am · 1:40 pm | |
| Sun 1 | 50 / 56 °F | 9 mph NNE | 1.0 ft | 2:23 am · 2:44 pm | |
| Mon 2 | 47 / 53 °F | 11 mph E | 1.2 ft | 3:38 am · 4:00 pm | |
| Tue 3 | 43 / 53 °F | 9 mph ENE | 0.5 ft | 5:03 am · 5:23 pm | |
| Wed 4 | 43 / 51 °F | 8 mph ENE | 1.2 ft | 6:22 am · 6:38 pm | |
| Thu 5 | 44 / 53 °F | 9 mph ENE | 1.2 ft | 7:23 am · 7:37 pm | |
| Fri 6 | 43 / 50 °F | 9 mph NE | 0.7 ft | 8:11 am · 8:25 pm | |
| Sat 7 | 38 / 48 °F | 6 mph ENE | 3.1 ft | 8:51 am · 9:06 pm | |
| Sun 8 | 45 / 51 °F | 9 mph ENE | 2.7 ft | 9:26 am · 9:42 pm | |
| Mon 9 | 51 / 56 °F | 11 mph SE | 2.8 ft | 9:59 am · 10:17 pm | |
| Tue 10 | 51 / 55 °F | 5 mph E | 1.9 ft | 10:31 am · 10:50 pm |
- Thu 29 Overcast 52° / 57° 2.6 ft
- Fri 30 Overcast 50° / 57° 2.7 ft
- Sat 31 Overcast 47° / 58° 1.4 ft
- Sun 1 Overcast 50° / 56° 1.0 ft
- Mon 2 Overcast 47° / 53° 1.2 ft
- Tue 3 Overcast 43° / 53° 0.5 ft
- Wed 4 Overcast 43° / 51° 1.2 ft
Each day comes from the best model covering this spot: regional ones first (HRRR and NBM in the U.S., AROME, ICON-EU), then ECMWF; day 16, NOAA GFS. Waves: Météo-France up to day 10, then ECMWF WAM, coarser and further offshore. High tides: our own tide calculation.
- The models They agree · high confidence for the next few days. See the models →
- Outlook Next few weeks, compared with normal: normal temperatures, normal rain and a slightly warmer sea. See the outlook →
- Normal Today, warmer than normal for late October (+2.5 °F; normal high: 55 °F). Climate by month →
Forecast from Open-Meteo (CC BY 4.0) with models from ECMWF, NOAA, Météo-France, DWD, Copernicus Marine and CAMS. Updated at 9:53 pm (local time).
The sun in Cemaes Bay
Sunrise and sunset
- First light 5:52 am
- Full dark 6:11 pm
- Civil dawn 6:33 am
- Civil dusk 5:30 pm
- Solar noon 12:02 pm (23° high)
- Daylight 9 h 44 min (−4 min)
- Evening golden hour 4:02 pm
- Full dark 6:11 pm
Golden hour and the day-night map
Today the sun is 92,359,559 mi away and looks 32′ 11″ across.
The moon in Cemaes Bay
Moon phase and position
Today the moon is 226,451 mi away and looks 32′ 47″ across.
Solunar periods
Today's activity: high- 12:40–2:40 am Major · the moon passes overhead · high activity
- 1:12–3:12 pm Major · the moon passes underfoot · high activity
- 10:18–11:18 am Minor · moonset · medium activity
- 5:00–6:00 pm Minor · moonrise · medium activity
According to solunar theory, fish feed more when the moon passes overhead or underfoot (major periods, about 2 h) and when it rises or sets (minor periods, 1 h). It works best around new and full moon.
Upcoming moon phases
2026 moon calendar →- Last quarter Sun, Nov 1 · 8:29 pmNov 1 in 4 days
- New moon Mon, Nov 9 · 7:03 amNov 9 in 12 days
- First quarter Tue, Nov 17 · 11:48 amNov 17 in 20 days
- Full moon Tue, Nov 24 · 2:54 pmNov 24 in 27 days
Perigee on October 28, 226,426 mi away, coinciding with the spring tides from October 26 to 28: they will be stronger than usual.
Where to fish in Cemaes Bay
Piers, ramps and tackle shops nearby
Map: OpenFreeMap · © OpenMapTiles · © OpenStreetMap contributors
- Pier Bach 0.3 mi
- Llyn Blodyn Fishery 8.4 mi
- Boat ramp 0.1 mi
- Boat ramp 3.4 mi
- Boat ramp 4.8 mi
- Boat ramp 6.5 mi
- Porth Amlwch 4.9 mi
- Tackle shop 4.4 mi
Within 9.3 mi. A spot may be missing or closed. Open the map on OpenStreetMap · Missing one? Add it to OpenStreetMap
Spots: © OpenStreetMap contributors (ODbL) and Overture Maps.
Water depth
Gentle slopeThe bottom slopes gently: 16 ft deep 0.3 mi from shore and 33 ft at 0.5 mi.
From the shoreline (700 ft from Cemaes Bay) out to sea, heading north.
How far from shore
- 16 ft deep0.3 mi
- 33 ft deep0.5 mi
- 66 ft deep0.8 mi
- 164 ft deepnot within 3.1 mi
For fishing, swimming and diving
- Shore fishing. Shallow, gradual bottom (16 ft at 0.3 mi): cast far from the beach and fish the high tide, when there is more water close in.
- Swimming. A very gentle way in with plenty of shallow water, good for kids. At low tide the water can be far out.
- Diving. Shore diving works here: 33 ft at 0.5 mi and 66 ft at 0.8 mi from shore.
Source: EMODnet Bathymetry DTM 2024 (CC BY 4.0), cells of about 380 ft; depth at the lowest astronomical tide. For reference only: not for navigation or anchoring.
Nearest lighthouse
West Mouse Pilots Beacon 4.3 mi west
Other lighthouses nearby: Amlwch Lighthouse (4.9 mi east).
Data from Wikidata. For reference only: not for navigation. Wikidata · Sources and licenses
Tides near Cemaes BayTides nearby
- Amlwch4.3 mi
- Bodedern8.5 mi
- Valley10.0 mi
- Holyhead10 mi
- Benllech11 mi
- Rhosneigr13 mi
- Aberffraw15 mi
- Malltraeth15 mi
- Llanfairpwllgwyngyll17 mi
- Llangoed17 mi
Cemaes Bay at a glance
- Town or city of about 1,187 people. Coordinates: 53.412° N, 4.452° W.
- It is 10 mi northeast of Holyhead, the main place in Anglesey. The sun rises at the same time and sets 1 min earlier than in Holyhead.
- The nearest tide station, Holyhead, is 9.7 mi to the southwest.
- Its coast faces north.
Questions about Cemaes BayQuestions
What time is high tide today in Cemaes Bay?
Today in Cemaes Bay there are high tides at 11:12 am (19.2 ft) and 11:37 pm (19.2 ft) and low tides at 5:00 am and 5:24 pm. Tide coefficient 92.
What time is sunset today in Cemaes Bay?
At 4:53 pm. There is light until the end of civil twilight, at 5:30 pm.
What time is sunrise tomorrow in Cemaes Bay?
At 7:11 am. First light comes at 5:53 am.
What phase is the moon today?
Waning gibbous, 92% illuminated. New moon on Mon, Nov 9 · 7:03 am.
When are the next spring tides?
From October 26 to 28, together with the lunar perigee: they will be stronger than usual.
What are today's solunar periods?
Major 12:40–2:40 am, Minor 10:18–11:18 am, Major 1:12–3:12 pm, Minor 5:00–6:00 pm. Today's activity is high.
What's the weather like today in Cemaes Bay?
Light rain, from 53 °F to 58 °F, with a gentle breeze from the south-southwest (9 mph) and a 100% chance of rain.
How is the sea today in Cemaes Bay?
Slight (Douglas 3): 2.6 ft waves with a period of 5.4 s from the southwest. The water is 55.8 °F.
When is the best time to visit Cemaes Bay?
The best time to visit Cemaes Bay is from June to August: highs of 63 °F to 66 °F, about 12 rainy days a month and 6 hours of sunshine a day.
Can I use this data for navigation?
No. These are predictions for fishing and leisure; for navigation, use the official publications.
Where this data comes from
Tide: Holyhead tide gauge (UK National Tide Gauge Network). This uses Environment Agency tide gauge data from the real-time data API (Beta), under the Open Government Licence v3.0; constants fitted by TidePlanet from a year of its readings. Sun and moon: our own calculation with astronomy-engine. Places: GeoNames (CC BY 4.0). Coastline: © OpenStreetMap contributors (ODbL).