There are four indicators that decide whether it's worth loading up the car. Learn where to find them, what they mean and how to pick the best sea for each type of fishing.
Sea state is the condition of the sea surface created by the waves, and it comes down to four values: the height of the waves, the period between them, the direction they come from and the wind. For anglers, these four numbers are what decide whether the trip is worth it and where it's safe to go.
There are two ways to ruin a fishing trip before you even leave the house. Hauling everything to a spot where the sea isn't cooperating or staying home on a day that was perfect.
Both cost the same and come from the same place. You open the forecast and you get a table with ten or twelve rows. You look at one or two and decide. The rest aren't there to fill space. Everyone looks at the height first, but it's the time between the waves that tells you more about the day you're going to have.
Where to Check the Sea Forecast
There are two sources that have all the information you need. Your national weather service is the official one. The Met Office, Météo-France, AEMET and the rest all publish a marine forecast with the sea state by coastal area, though how far ahead it runs changes from one country to the next. Windguru is used by many anglers because it puts everything in a single table, hour by hour.
Those same services also issue warnings when the sea turns dangerous, under the heading of coastal events, and MeteoAlarm gathers them for the whole of Europe on a single map. When there's an active warning, the decision is no longer about fishing, it's about safety.
1. Wave Height: The Number That Misleads
The value in meters that the forecast gives you isn't the size of the waves you'll find. It's an average, calculated only from the highest third of the waves, leaving out all the small ones. Even so, there are always sets that go well above that value. Expect double what's forecast. In a 1.5-meter sea, the biggest ones that morning get close to 3. That's why some people get caught by a wave on a day that looked small.
The waves don't all arrive the same. They come in sets, and as a rule the groups of bigger waves are separated by calmer stretches. And fifteen minutes can pass between one big set and the next. So before you pick your spot, stay twenty minutes watching the sea. If you only stay five, there's a good chance you'll never see the biggest one of the day, and that's exactly the one that can catch you out on the rocks.
2. Wave Period: The Number That Decides the Day
The period is the time, in seconds, between one wave and the next. Two meters at 7 seconds is nothing like two meters at 14. This number tells you where the sea in front of you comes from. If it was created by the wind blowing right there, the period is short. If it came from far away, it's long.
Up to 9 seconds: wind swell
These are waves created by the wind blowing at that moment, right there in front of you. They arrive messy and ruin your bait presentation. The good news is that they die down with the wind. If the wind eases in the afternoon, the sea eases too.
Over 15 seconds: ground swell
These are waves that came from far away, born in a storm thousands of kilometers from here, often in the North Atlantic. They arrive in clean, well-spaced sets and don't depend on the wind that's blowing, so there may not be a breath of wind and the sea can still be big.
Between 9 and 15: it depends on the height
It's the most common range in the forecast and the one that forces you to decide. The height settles it, and the test is this: when the waves are big, it takes a lot of local wind to raise them, so it's wind swell. When they're small but the period is long, that energy came from far away.
From this comes the practical rule that works for any day: wind swell calms down when the wind calms down, ground swell doesn't. If the problem is wind swell, it's worth waiting for the afternoon. If it's ground swell, waiting solves nothing.
The period doesn't just measure the time between waves. It measures the energy they carry. A ground swell wave has travelled thousands of kilometers building up force, and it reaches the coast with far more energy than a wave the same size created by the wind right in front of you.
That's why ground swell arrives with much more power. It breaks farther out and runs higher up the rocks, and that's why one meter at 15 seconds is more dangerous than two meters at 7. If you're fishing from a rock ledge, this is the number that decides whether you go or not.
3. Direction: Where You Can Fish Today
It's shown as an arrow in the swell forecast, and it's what decides where you can go. But careful, don't confuse it with the wind direction, which is shown in another row.
On Atlantic-facing coasts, the swell almost always comes from the western quadrant, somewhere between west and northwest. On a coast that faces south or east the exposure is completely different, and that's why the same numbers make for completely different days.
What matters about each spot is its exposure, in other words, which way it faces. A spot sheltered from the northwest fishes well on a day when the one next to it, facing straight out to sea, can't even be reached. And both are in the same forecast, with the same numbers.
4. Wind: Focus on the Gusts
The forecast gives you two values: the average wind speed and the gusts. What ruins your cast is the gusts.
Then there's the wind direction, and here there are three scenarios:
- Offshore wind, blowing at your back, is the best of all. It flattens the surface of the water and carries your cast. But if it's too strong, it lifts the line so much that you stop feeling the bite. Which compass direction that is depends on where you're standing: on a west-facing coast it's an easterly, on a south-facing one it's a northerly, so check which way your beach faces.
- Onshore wind kills your distance and lifts the line.
- Crosswind is the worst for feel, because it puts a belly in your line, that curve that cuts off your contact with the bait.
And watch out for the units in the table! A knot is almost 2 km/h, so 15 knots is about 28 km/h.
Sea Conditions for Each Type of Fishing
Surfcasting
It's the type of fishing that can handle the most sea. Beach fishing is made for rough seas, because it's precisely in those conditions that fish come in to feed. With a good swell, the water gets well oxygenated and the bottom is stirred up enough to get them hunting for food.
With too little sea, the water settles and turns crystal clear, and the fish get wary. On the international sea state scale that's a rippled or a smooth sea, and it doesn't go above half a meter. It's a beautiful sea to look at, but it's not ideal for casting.
As for wind, it's also the type of fishing that tolerates it most, especially when it's offshore. A light breeze helps more than it gets in the way.
Float Fishing
On the rocks, the margin is the narrowest of all the types of fishing, and here the decision is about safety. Height alone isn't enough to decide, because the enemy is the long period. A small sea with well-spaced sets sends water over the ledge without warning, and that's the situation that catches people off guard.
With wind, it's not worth it either, because the float starts dancing and you can't tell when a fish bites.
Spinning
Both extremes punish Spinning. A glassy sea makes the European Sea Bass cautious, giving it time to inspect the lure and swim off without touching it. A sea that's too big keeps the lure from working the way it should. It's in water with a bit of color that it strikes without thinking twice.
As for wind, it tolerates less than Surfcasting, because the lure is light and stops going where you want long before the sinker stops holding. With an onshore wind, it pays to switch to soft plastics with more vibration.
Boat Fishing
On board, height matters less than you'd think. What ruins the day is a short period, because the hull never stops moving. A small, choppy sea is much less fishable than a bigger one with well-spaced sets. What you're after is light wind and a long sets.
And stay away from a cross sea, with the wind blowing from one side and the swell coming from another. The boat rocks in two directions at once, and that's when fishing gets complicated.
What About the Tides?
The four numbers above tell you what the sea is doing. They don't tell you when the fish will be feeding, and that's decided by the tide. A complete fishing forecast crosses the sea state with the tide table for your area, so check both before you head out.
As you've probably figured out by now, there's no such thing as a good sea. There are conditions that come together for a particular type of fishing. At Casa Favais, we've been hearing this conversation at the counter every day since 1977. If you have questions about what gear can handle the sea you usually fish, get in touch.
Frequently Asked Questions
How do you know if the sea is good for fishing?
Look at all four values at the same time, because none of them decides on its own. The wave height tells you the size, the wave period tells you how much force that size carries, the direction tells you which spots stay sheltered and the wind tells you whether you can cast where you want.
Are rough seas good for fishing?
On the beach, a rough sea stirs up the bottom, oxygenates the water and gets fish hunting for food, so it's good. On the rocks it's a different story, and there the period matters more than the height: long, well-spaced sets run up onto the ledge without warning even when the sea is small.
What's the best wind for fishing at sea?
An offshore wind, blowing at your back with the sea in front of you, because it flattens the surface and carries your cast. And always look at the gusts rather than the average, because they're what ruin your cast.
What's the difference between wind swell and ground swell?
Wind swell is the sea created by the local wind and it arrives messy. Ground swell comes from a distant storm and arrives in clean, well-spaced sets. You can tell them apart by the period: up to 9 seconds is wind swell; over 15 is always ground swell.
And you, which number do you look at first when you open the forecast? Tell us in the comments and send us photos of the sea you found on Instagram, @casafavais.