AIS Offshore: The Silent Advantage — and the Hidden Trap

The Night We Were Beaten by a Light

God created the world in six days.

Offshore sailors then spent the next few thousand years navigating it using one tool.

Their eyes.

In or around 1983, I was a young sailor trying to get a foothold in the offshore racing world. I had just returned from Newport, Rhode Island, where the Australians had just won the America’s Cup with their remarkable wing-keeled 12-metre. I had been crew on the British yacht Victory with Pete de Savary, the team boss.

When I got back, I was lucky enough to compete in one of the Royal Yachting Association crew selection schemes—what many will remember as Crew Match —which, at the time, was one of the few real gateways into the yacht racing scene. I made the final but didn’t win and had to return to my day job in the Royal Navy.

Start of offshore race in 1981 Admiral’s Cup

But that’s how I ended up sailing with Brian Saffrey-Cooper and his wife Pam aboard Dragon —a serious Admiral’s Cup one-tonner. Proper boat. Proper campaign. No passengers.

Brian was an absolute legend, and his boat Dragon was part of the team that won the Admiral’s Cup in 1981. They competed alongside team captain Robin Aisher on Yeoman XXIII and Peter de Savary on Victory of Burnham . Dragon was a one-tonner designed by one of the world’s most brilliant racing yacht architects, Ed Dubois.

So I was amazed when I got a call from Pam asking if I could join them on Dragon . I was brought onboard to helm and contribute tactically. I didn’t say much, as you might imagine, and just tried not to get it wrong. It was an amazing opportunity, and the following story has stayed with me for that very reason—I was under pressure to perform.

We were racing to Saint-Malo in the RORC race, also known as the Cowes–Dinard Race, as Dinard was the yacht club across the bay where all the race yachts anchored after finishing, before the marina was built, waiting for the tide to open the lock into the St Malo basins.

So back to the story—and why it links to the tech world of AIS.

In 1983, we didn’t have GPS, plotters, GRIB files, phones, or satellite dishes.

Just paper charts, a B&G log, an echo sounder, a pencil—and what you could actually see.

As dusk fell, we locked onto our nearest competitor ahead. You always did that in those days. Pick a boat. Track it. Build your race around it.

I was on the helm with a four-hour watch ahead of me. It was a beat—cold and wet—and the Casquets Lighthouse was still 45 miles away. It was pitch black, but I could see a few stern lights and a couple of red and green lights to port and starboard, which we were passing quickly.

I focused on one stern light I knew belonged to a similar, fast one-tonner ahead. I think it was a French boat, as I’d caught a glimpse of her sail number before it got dark.

So we had his stern light.

White. Steady. Just far enough ahead to matter.

Then, slowly, it began to fade.

At first, you question yourself. Then you check trim. Then heading. Then you start making small, slightly desperate changes—because the conclusion is obvious.

He’s sailing away from you.

And I was on the helm. There were comments on deck, a lot of trimming, and plenty of suggestions. They probably all thought it was my inexperience.

We pushed harder. Re-trimmed. Re-thought everything.

Nothing stopped that light getting dimmer… and dimmer… until eventually it disappeared over the horizon.

Gone.

We thought we’d been outsailed. Properly beaten.

Brian came on deck and asked how we were doing. After a long silence, he was told we had lost the boat ahead. Brian, however, seemed untroubled and let me stay on the helm while quietly checking the boat speed and trim.

Only later did we find out what had actually happened. (I think Brian already knew about this trick, and we never found out if they beat us or not—we only thought we knew who they were, and certainly couldn’t prove anything. After all, it’s a gentleman’s sport… the sport of kings.)

This is what they did…

They’d fitted a dimmer switch to their stern light.

Someone onboard was simply winding it down—just enough, just slowly enough—to make it look like they were pulling away.

It didn’t change reality.

It changed perception.

And that was enough to change behaviour.

From Eyeballs to Electronics

In those days, offshore awareness was brutally simple.

You saw what was there, or you didn’t.

Navigation lights gave you range, but limited range. Three or four miles was typical. Beyond that, boats simply vanished. Your mental model of the race was built on fragments, lights, bearings, intuition.

Then came Decca, then GPS, and eventually, AIS.

Suddenly we could “see” everything, or so it felt.

Targets at 10, 12, 20 miles. Course, speed, CPA, identity.

Certainty.

Except the early years of AIS offshore were, frankly, a mess.

Before it became embedded in offshore racing rules, adoption was patchy. Some boats had it. Many didn’t. Some transmitted. Others didn’t. Fishing vessels were inconsistent.

And then there was the racing behaviour.

Boats would run AIS during the day… then quietly switch it off at dusk.

Chart table switch. Hidden. Off.

The boat you’d been tracking all afternoon simply disappeared. The stern light dimmer switch was back with a digital reboot!

Out of range? Failure? Tactical move?

You didn’t know.

Different technology.

Same problem.

You’re making decisions based on what you think you’re seeing.

And That’s the Point

That fading stern light and a modern AIS screen are not so different.

Both look authoritative. Both influence behaviour. Both can be wrong—or incomplete.

Which brings us to AIS today.

What AIS Gets Brilliantly Right

AIS has transformed offshore racing.

For most race boats, especially IRC and double-handed, it is now the only real-time electronic awareness tool onboard. Very few carry radar effectively at race pace.

AIS becomes the picture.

And that’s exactly where the danger starts.

AIS has fundamentally improved safety and performance.

Early identification of traffic. Clear course and speed. CPA without guesswork. Direct communication.

And most importantly, confidence.

The Problem: It Looks Like the Whole Picture

AIS is clean. Precise. Convincing.

But it’s not reality.

It’s a filtered, delayed, incomplete snapshot.

AIS feels like truth. But it may not be.

Range: You’re Sailing Inside a Bubble

AIS is VHF-based—nominally line-of-sight, but inconsistent.

Big ships (Class A, 12.5W): 20–30 miles. Race yachts (Class B, 2–5W): 8–15 miles.

Sometimes more. Sometimes less.

You are not seeing the whole racecourse. You are seeing a moving bubble around your boat.

Update Rates: The Hidden Lag

AIS is not exactly real-time.

At 20 knots closing speed, a vessel moves over 300 metres between updates.

CPA assumes constant course and speed.

Offshore, that assumption is often wrong.

CPA is not a prediction. It’s a projection.

Tide: The Distortion Nobody Talks About

AIS shows course over ground—not through water.

In tidal environments, that matters.

AIS shows what the boat is doing over the seabed. Racing decisions are made through the water.

The Biggest Tactical Error: Sailing the Screen

This is where races are lost.

You alter early. You play safe. You avoid a problem.

But you give away leverage. You break routing. You lose miles.

AIS didn’t make the mistake.

You gave it authority it doesn’t deserve.

The real question offshore:

“What is the fastest route—and how do I manage traffic within it?”

AIS Only Shows What It Sees

AIS is cooperative.

If it’s not transmitting, or you’re not receiving it, it doesn’t exist on the screen.

Small vessels. Fishing gear. Weak signals.

A quiet screen does not mean empty water. It means incomplete information.

Human Factors: The Real Trap

AIS introduces automation bias.

At night, it reduces anxiety but narrows attention.

Crews stop looking outside.

The danger isn’t that AIS is wrong. It’s that it makes you stop looking.

The FirstBeat Reality Check

AIS Perception vs Reality

AIS IS A PROJECTION NOT A PREDICTION

Most sailors react to AIS.

The best manage it in tandem with all other tools and, number one, the eyeball.

A Simple Offshore Framework

AIS is early warning, not full awareness. Assume something exists outside the screen. Never let a vector override your plan. Delay decisions, but not beyond control. Keep looking outside.

Sail the racecourse first. Manage AIS second.

Bottom Line

AIS is indispensable.

But so was that stern light.

It looked real. It drove behaviour. It was wrong.

AIS is no different.

It makes you safer. It can make you faster.

But only if you understand what it is:

A short-range, imperfect, delayed view of a much bigger game.

AIS doesn’t lose races. Believing it tells you the whole story does.