Night Watch
Night Watch support
Last updated 15 September 2026.
Night Watch identifies a vessel from the lights or day shape you can actually see, offline, with the Rule number carried on every answer so you can check the source rather than trust the app.
Why it gave me more than one answer
Because a real sighting is usually partial. Lights are obscured by rain, by a headland, or by the vessel's own aspect, and a partial stack genuinely matches more than one signature.
So the app returns every candidate, most specific first, rather than choosing. One that picked a single answer and stated it confidently would be most wrong exactly when visibility is worst, which is when somebody is using it.
Why it says nothing about who gives way
That is a scope decision, not a missing feature. This app answers what you are looking at, which is a matter of fact, and stops there.
Telling somebody they are the stand-on vessel and should hold course is a collision-avoidance instruction. Rule 2 makes clear that nothing in the Rules exonerates any vessel from neglecting ordinary good seamanship or the special circumstances of the case, and Rule 17 requires even the stand-on vessel to act when collision cannot be avoided by the other alone. An app cannot see the other vessel's aspect, its speed, or the sea room either of you has.
Why nothing matched
Some stacks correspond to no vessel in the Rules, and the app says no match rather than falling through to the nearest thing. A near answer is worse than none here, because the order of a stack is the whole meaning: red over white and white over red are different vessels, and a pair the wrong way round turns a fishing boat into a pilot vessel. Enter the lights top first.
Entering what you can see
Tap the all-round lights in the order they are stacked, then mark whatever else is visible: sidelights, a sternlight, a yellow towing light, or masthead lights. In daylight you can pick a day shape instead. A partial observation is a valid one and produces a list rather than an error.
Inland and International
The signatures are transcribed from the Navigation Rules (Amalgamated) published by the US Coast Guard Navigation Center, and the Rule 21 arcs are listed on the About screen, because whether a light shows over 135 degrees or 225 is what tells a bow from a stern. Inland and International Rules differ, and where they do the difference is noted on the item itself.
What Night Watch is not
- A reference tool, not an aid to navigation. It does not replace a lookout, a chart, or the Rules themselves.
- It summons no help and contacts nobody. There is no emergency function of any kind, and nothing in it should be relied on in place of your own radio and your own judgement.
- Not affiliated with, endorsed by, or connected to the United States Coast Guard or the Coast Guard Auxiliary.
Practice, and the unlock
Identifying is free, always, for everybody. Charging somebody to find out what the lights ahead of them mean, at night, is not something this app will do.
What is paid for is practice: drilling the signatures until you know them without reaching for a phone, with a record of which ones you have got right. That is a study tool for somebody revising, which is a different situation from standing on a foredeck at two in the morning.
The unlock is a single one-time purchase, not a subscription, so there is nothing to cancel and nothing renews. The price is shown on the unlock screen inside the app, which reads it from the App Store for your country.
Restoring it
After a reinstall or on a new device, use Restore on the practice screen. It asks the App Store what your Apple ID already owns. If it reports no previous purchase, check you are signed in with the Apple ID that bought it, because that is the cause almost every time.
If a purchase fails
If the App Store cannot be reached, no payment is taken, and identifying lights keeps working offline regardless. Try again when the device has a connection, or use Restore if you have bought the unlock before. Apple is the merchant of record, so refunds are requested from Apple at reportaproblem.apple.com.
Your data
There is no account, no sign-in and no server. Nothing you tap is uploaded anywhere. The app stores exactly one thing, which signatures you have answered correctly in practice, and it stores it on that device only. Deleting the app removes it. Nothing is shared with anyone, because there is nowhere for it to go.
The whole reference works with no connection at all, which is the point of building it this way.
Contact
One person reads that, so a reply may take a few days.
Night Watch is published by Jeffrey L Carrier.