How SurfCheck works
A surf forecast tells you what the swell is doing out at sea. What happens next depends on the seabed under your break. SurfCheck gives you both: an hourly forecast for every spot, and the surveyed reefs, sandbars and channels that turn that swell into a wave.
From the open ocean to your break
The forecast
Swell height, period and direction, wind and tide, every hour for every spot, with a score, and webcams where there are any.
The seabed
Depths from national seabed surveys, down to a few metres apart. Where nobody has surveyed, we fill the gap and show it grey.
The wave model
A wave model runs over that seabed in your browser. You watch swell slow, bend round the reef and break.
The check
We compare where the model breaks waves with satellite photos of where the sea actually broke.
See what's under the break
Ireland has mapped its seabed in more detail than most countries, through INFOMAR, the national programme run by Geological Survey Ireland and the Marine Institute. Survey ships and aircraft have measured the depth every few metres along much of the coast.
We've turned that survey into 3D scenes of Irish breaks, plus Supertubos in Portugal from its own coastal survey. The reef off Mullaghmore Head, the sandbars at Strandhill, and Tramore Bay, shallow for kilometres out, are all there to spin and zoom.
Then press Run swell. The waves you see are a model, drawn with their height stretched so you can see them, but the seabed is the survey, grey where we had to fill it in.
The seabed is a lens
Swell can cross an ocean in a straight line, then change direction in the last few kilometres. The reason is depth. Once the water is shallow enough for a wave to feel the bottom, it slows down, and the shallower the water, the slower it goes.
A crest rarely meets shallow water all at once. The part over a reef or a point slows first while the rest keeps going, so the whole crest swings round towards the shallow ground. Energy gathers where the crests bend together and spreads out where they bend apart. The swell brings the energy; the seabed decides where it lands. That is why one point can be firing while the bay beside it is flat.
Why long-period swell wraps further
A wave starts to feel the bottom at a depth of about half its length. An 8 second swell is about 100 m long, so it barely notices the bottom until the water is 50 m deep. A 16 second swell is about 400 m long and starts slowing in 200 m of water, often kilometres further out. It has more distance to bend, so it wraps further round points and into corners that short-period swell never reaches.
The rule only holds for one swell at a time. Real seas mix periods and directions, and currents bend waves too. Our model shares those limits; see what it can't tell you.
| Water depth | 8 s swell | 16 s swell |
|---|---|---|
| 200 m | 12.5 m/s | 24.9 m/s |
| 50 m | 12.4 m/s | 19.2 m/s |
| 20 m | 11.1 m/s | 13.3 m/s |
| 10 m | 8.9 m/s | 9.6 m/s |
| 3 m | 5.3 m/s | 5.4 m/s |
Change the swell and watch the break respond
The Wave Lab lets you set the conditions. Pick a break, then move swell height, period and direction, wind and tide. The sea redraws as you go.
Beside it, a plain readout: how big the waves get at the peak, whether they spill or plunge, whether the wind is cleaning them up, and an experimental "Will it barrel?" with its reasons.
Every break states how much of the seabed under it was measured and how much was filled in, graded A to C. Where the survey is too thin, the lab says "Not reliable here" rather than guess.
Checked against the real sea
A model that is never checked is a guess. So we checked ours against the only record we could find of where waves really break that covers every coast: satellite photos.
The European Sentinel-2 satellites photograph the coast every few days. On clear days since 2021, the whitewater shows exactly where the sea was breaking. For each photo we ran the model with that day's swell and tide and measured how far its surf zone sat from the real one.
50 breaks, October 2026. Best on well-surveyed reefs and points, mostly within 20 m. Weakest in big Irish and Moroccan bays, where the survey stops short of the beach and the bay takes the edge off the swell. We publish the misses too.
What it can't tell you
Today's sandbars
Every survey is a snapshot from the year it was taken. Reefs barely change. Sandbars move with every winter's storms.
Currents and rips
The model has no currents, so it can't show rips, tidal races or wind against tide. Read the rip currents guide.
Sheltered bays
In deep bays the model is fed the open-ocean swell, so it breaks waves further out than the sea does. Lahinch, Inchydoney and Tramore say so on the page.
Who should paddle out
The model shows a wave's shape, not whether it's a good idea for you. That depends on you, the day and the people in the water.
Not a safety or navigation service. Check the forecast, watch the water before you go in, and never surf alone. In an emergency at sea in Ireland or the UK, call 112 or 999 and ask for the Coast Guard.
Surf safety · Rip currents · RNLI water safety · Water Safety Ireland
The seabed under every scene
Tap one to open it in 3D.
Common questions
Are Seabed 3D and the Wave Lab forecasts?
No. The spot pages carry the forecast: swell, wind and tide, every hour. Seabed 3D and the Wave Lab are teaching tools. They show how a seabed shapes swell. They don't know today's sandbars, currents or crowds, so never use them to decide whether to paddle out.
Where does the seabed data come from?
In Ireland, from INFOMAR, the national seabed mapping programme run by Geological Survey Ireland and the Marine Institute. Elsewhere from EMODnet, the Environment Agency and UK Hydrographic Office in England, NOAA in the US, New South Wales in Australia, and Portugal's coastal LiDAR survey. All open data, credited on every view.
How accurate is the wave model?
We check it against satellite photos of whitewater. At 50 breaks (October 2026), 30 matched closely, 11 fairly, 7 poorly and 2 had too few clear photos to judge. It is best on well-surveyed reefs and points and weakest in big bays where the survey stops short of the beach.
Are the sandbars up to date?
No. Every survey is a snapshot from the year it was flown or sailed. Reefs barely change. Sandbars move with every winter's storms, and beach breaks carry that warning.
Does SurfCheck cost anything?
No. SurfCheck is free, with no login, no paywall and no ads.