Channel Marks
Channel Marks support
Last updated 15 September 2026.
Channel Marks tells you what a US buoy or beacon means and which side to pass it, with the handbook paragraph behind every mark, and it works with no signal.
Why the answer changed when I switched heading
Because it should. "Red, right, returning" is half a rule: every lateral mark means the opposite thing depending on which way you are going. The same red nun you keep to starboard coming in must be kept to port going out.
That is why the heading is a switch pinned at the top of the screen rather than an assumption buried in the answer. Set it to returning or seaward once, and every mark below is answered the right way round. Non lateral marks, such as safe water, isolated danger, special and regulatory marks, do not change with heading at all, and the app does not pretend they do.
Why it gave me several possible marks
When you narrow by colour, shape or topmark, the app returns every candidate that still fits, most specific first. A mark seen at distance, at dusk, or against a low sun usually gives you colour or shape but rarely both. An app that picked one would be at its most confident exactly when the sighting was at its worst.
What it will not do
It tells you what a mark means. It does not tell you where the channel is. It cannot see your chart, your position, or your heading beyond what you tell it.
The handbook is blunt about the two things that matter here, and so is the note on every result: aids to navigation should never be relied on exclusively, and a buoy may not be "watching properly", which is to say it can drag, sink or sit well off its charted position.
I am outside the United States and the sides are wrong
They are reversed, and that is expected. Channel Marks covers the US system, IALA-B. Most of the world uses IALA-A, where red and green mean the opposite sides. Cardinal marks, used in Canada, Bermuda and the Bahamas among others, are not covered at all.
Where the marks come from
Every mark carries its paragraph reference in the Boat Crew Training Handbook, Navigation and Piloting, Chapter 2, Aids to Navigation. Nothing is written from memory, so you can go and read the source.
This is a reference tool, not an aid to navigation and not a substitute for a chart. It is not affiliated with, endorsed by, or connected to the United States Coast Guard or the Coast Guard Auxiliary.
Practice mode
Reading the marks is free, now and always. What the purchase buys is practice: the Practice tab drills every mark, shows you a colour and a shape and asks which mark it is, then gives the side to pass and the handbook paragraph. It counts how many of the marks you have learned and keeps that count between sessions.
It is one payment, not a subscription, so nothing renews and there is nothing to cancel. The current price is shown on the unlock button inside the app, which reads it from the App Store for your country.
Restoring a purchase
On a new phone or after a reinstall, tap Restore a previous purchase on the Practice tab. It is shown whether or not the app believes the device is unlocked. If nothing is found, check that you are signed in with the same Apple Account that bought it, which is the cause almost every time.
Refunds
Apple is the merchant of record, so refunds are requested from Apple at reportaproblem.apple.com. We cannot issue one.
Your data
There is no account and no sign-in screen. There is no server, no analytics and no network call of any kind, so nothing about you is collected or uploaded. Practice progress is written to storage on your own device and is removed with the app.
Contact
One person reads that, so a reply may take a few days.
Channel Marks is published by Jeffrey L Carrier.