Watching one particular vessel takes three steps: find her, open her, follow her. After that the e-mails do the watching for you.

Find her

Use Search boats rather than hunting across the chart. The search box sits beside the account icon on a computer, and behind the magnifying glass at the top of the screen on a phone.

You can search by name, MMSI, call sign or IMO number. In practice:

• A name is the way in for most people, and it is enough on its own. You do not need a number to follow a vessel.
• An MMSI is the nine-digit number an AIS radio broadcasts. Typing all nine digits matches one vessel and nothing else, which settles it when several vessels share a name.
• A call sign or an IMO number widens a search rather than carrying it. Both are reported by a minority of vessels, so a search on one can come back empty for a vessel that is plainly on the chart.

Each result carries what you need to tell two vessels of the same name apart: her type, her length, her flag, the water she is in, and how far away she is and in what direction. Distance is measured from your own boat when one is linked to your account and has reported recently, and otherwise from the middle of the map you are looking at; the results say which of the two they used, and they leave the distance off rather than measuring from a position too old to mean anything.

What her panel tells you

Tap a vessel and her panel opens with what AIS reports about her: her name, her MMSI, what kind of vessel she is, her flag (the country she is registered in), her speed and course, whether she is moving or stopped, when she was last heard, and her length and beam (how long and how wide she is).

Some boats carry two extra lines, an AIS class and a destination. Those come from boats reporting their own details through Saillogger rather than from the AIS feed, so most traffic does not have them.

When she was last heard is the number to read. Everything above it describes the moment of that report, not this moment.

• 24h track draws where she has been over the last day, as AIS heard her, and Fit track frames the whole line.
• Her photos open full screen, with the count on the cover so you know how many there are. Vessel photos covers the catalog and how to add to it.
• Follow and Message are on the same row of actions. Message needs somebody on the other end: it reaches the AIS Fleet member who has linked that boat to their account, or her Saillogger owner. Most traffic on the chart is neither, so there is nobody there to write to, and that is the ordinary case rather than a fault.
• The panel collapses to a slim bar when you want the chart back, and the vessel stays selected.

There is no ETA, no port-call history and no track older than the last day. The live vessel map explains what the map itself can and cannot show you.

Follow her

Following is one-way and needs no approval from anybody. There are two ways to start:

• Tap the vessel on the map and press Follow on her panel.
• Open Following in the map's top-right controls and choose Find a boat to follow, which searches the same four ways.

The Following panel lists every vessel you follow, including the ones with no recent position, with a line each on where she is and when she was heard. Tapping a row takes you to her on the map, Show all on the map frames the lot, and Unfollow on the row ends it and frees a slot.

A follow does four things at once, which is why it is worth a slot: she is put on your map wherever she is, the type filter can never hide her, her marker stays at her last known position instead of dropping off the chart, and she e-mails you when she leaves and when she arrives. How many you can follow depends on your plan; see What it costs.

If she is not there

• "We are not tracking MMSI ... yet." No receiver has reported that number to us, so there is nothing to follow yet. Follow it anyway asks the AIS network to watch for it. That is not a follow: come back and follow her once she appears, which is the step that starts the e-mails. Worth checking the nine digits first, since a typo looks exactly like a vessel we have never heard.
• "No boats match that." Either the name she broadcasts differs from the one you typed, or no receiver has ever reported her to us. Try a shorter, more distinctive piece of the name. If you can get her nine-digit MMSI, searching that settles it either way.

A vessel with no AIS transponder is not on AIS Fleet at all, whatever else she carries.

Departure and arrival e-mails

This is the part that means you do not have to keep a map open.

• When she gets under way, the e-mail says she has departed, names where she left from when the place resolves, and carries a map of where she is.
• When she arrives, it names where she got to, and where the passage began when we can tell.
• A vessel that keeps her log with Saillogger and shares it names those places from her own logbook, and, where her owner publishes her individual trips, brings a map of the passage she has just completed. Her owner's photo of her leads the message where there is no map to show.
• Every one of these e-mails links straight to that vessel on your map.
• There is no digest. Three trips in a day means six e-mails, a departure and an arrival each time.

Notification settings, in the account menu, has a switch for each kind of e-mail: Followed boats, New followers, Direct messages and Fleet messages. They all start on, on every plan including the free one, and each of those e-mails carries a link back to that screen. Sign-in codes and the answer to a boat claim are not on that list: they are sent because you asked for something, and they arrive whatever the switches say.

Following a cruise ship or a ferry

Large passenger ships carry AIS and are heard by shore receivers whenever they are near a coast, which is most of a typical itinerary, so following one usually means an e-mail as she leaves a port and another as she reaches the next one. Coverage of big ships is good, so searching the ship's name is normally all it takes to find her.

Expect that to be frequent. A ship calling somewhere most days is roughly two e-mails a day for the length of the voyage, and a working ferry is far more than that. It is worth thinking about before you follow one, and Followed boats in Notification settings is the switch that turns the lot off.

On a longer ocean leg she can go quiet for days and reappear as she comes back into range. A marker that has not moved is telling you when she was last heard, not that she has stopped.

Boats that log with Saillogger

Some of the boats on the chart keep their logbook with Saillogger. When the owner shares it, her panel carries more than AIS broadcasts:

• Their own photo of the boat, published from their Saillogger profile.
• Her journal: the dated notes and photos posted from the trip.
• Show track: the real logged voyage, drawn from her own log rather than from AIS. It is the passage she is on now, not her season and not her back catalogue.
• Her own position reports, sent from aboard whenever she has an Internet connection, so she can keep moving on your map where nothing ashore is receiving her.

All of it is the owner's choice, made on their own sharing settings, and it is re-checked every time you look rather than fixed on the day you followed her. Two separate switches sit behind it:

1. Sharing and Live Tracking & Monitoring decide whether you get the detail at all: the journal, the logged voyage and their photo of the boat.
2. Update your position on AIS Fleet decides where the marker itself comes from: her own reports, or only what AIS receivers hear.

If the boat is password protected

Some boaters put an access password on their pages. Following such a boat offers you the choice: enter the password and you see everything they share, or follow with AIS positions only. You can enter it later from her panel, and if the owner changes the password you are asked for the new one.

A boat her owner keeps private is followed the way any AIS vessel is, showing her broadcast position and nothing of the owner's own.

If a boat's journal and track disappear one day, the ordinary explanation is that her owner changed what they share or changed the password, and not that anything has happened to her.