Sea Traffic

Small craft keep the water near the coast busy. They only appear where there's coast within a few km of you, so out on the open ocean you'll only meet the big ships.

• Every boat stays in water deep enough for it. Each leg is checked before it's taken, and a few times a second the boat looks ahead and turns away from shallows, land, piers and breakwaters. The checks are fine-grained (rays straight down onto the ground, the sea floor and harbour structures), so boats can work close inshore.
• Boats keep clear of each other, of the big ships (they always give way) and of you. When you're low over the water (landing on it, taking off from it, or in a boat) they also stay out of the stretch of water ahead of you. Ferries hold their course and slow down until the way is clear.
• Lights at night, following the rules of the road for small craft:
  • sailboats: red/green sidelights and a white stern light under way, a white light at the masthead at anchor;
  • speedboats and jet skis: an all-round white light and sidelights;
  • fishing boats: red over white all-round lights (a vessel fishing), sidelights, a stern light and deck working lights;
  • the motor yacht and tugs: masthead, sidelights and stern light, anchor light when stopped;
  • ferries: two masthead lights, sidelights, stern light, rows of lit windows and deck lights.
• Lightweight, like the big ships:
  • small boats are hidden beyond a few km, cast shadows only up close, and their wakes only run within 2.5 km of you;
  • jet skis and sailboats get a foam-only wake;
  • boats left behind are removed and new ones appear around you, so the count stays capped.
• Wakes are sized to the boat. Jet skis and sailboats leave foam only, with no wave. A fishing boat raises about 10 cm of wake wave and tugs about 25 cm. Speedboats and the yacht raise up to about 30 cm, and only at speed. Ferries raise a moderate wake of about 60 cm. The wave fades during hard turns, so a boat doing doughnuts leaves a ring of foam rather than a ring of wave.
• Single player, or the host in multiplayer only (as scenery), as with the other ships.

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Harbours come from SeaTraffic's port list (plus a few harbours that aren't ports of call, such as the Bannock Industrial naval yard) and from the game's own world objects with port, pier, dock, harbour, quay, wharf, jetty or marina in their names, as they load near you. Cranes and lighthouses are found by name too. Parts of a location that the game's occlusion culling is hiding at that moment (because they're behind a hill from where you are) are included, so a harbour that loads while you're far away is still found in full.

When you come within a few km of a harbour, SeaTraffic maps it once in the background, at 8 m resolution, with rays straight down. Each spot is classed as open water, land, a low structure (pier, quay, dock) or a tall one. Quays are the straight edges where a structure meets open water. Piers and jetties are the long, narrow decks with water on both sides, also where they join a quay. Ships are sized to fit their berth, and are only placed where the whole hull, plus a margin, lies over open water. So they never sit on land or cut through a pier. Everything is chosen from the harbour's name, so ships moor at the same spots every time.

The log (BepInEx/LogOutput.log, lines starting with Harbours:) lists every harbour, quay, pier head, crane, lighthouse and moored ship found. Harbour lights are also saved in BepInEx/cache/SeaTraffic/harbour-lights.txt, so they show from far away on later flights.

Settings and controls live in the Gravy Mod Menu (Sea Traffic tab) if that mod is installed. It shows:

• live status: how many fleets are out, the sea-lane map, and what each fleet is doing (speed in knots, distance);
• the small boats around you by type, and each ferry (where it's bound, speed, distance, or when it leaves);
• how many harbours were found and mapped, docked ships, how many lights are drawn, and which vessels you can hear;
• Spawn Cargo Ship, Spawn Carrier Group, Spawn Attack Boats, Spawn Small Boats, Spawn Ferry, Despawn All, Rebuild Sea Lanes and Rescan Harbours buttons;
• every setting below.

Without it, edit the .cfg file.

The spawn buttons put the new fleet a few kilometres away, ahead of you if there is open water there. Spawn Small Boats adds three small boats within 2.5 km (if there's coast). Spawn Ferry puts a ferry on the nearest crossing. Despawn All clears the sea, but the counts in the Traffic and Small Boats settings refill it within seconds: set them to 0 (or turn Enabled off) to keep it empty.

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Experimental online. This mod runs in multiplayer, but it still has bugs there that aren't fixed yet. It works best in single player for now.

Host only. Ships and boats only exist on the computer that spawned them; nothing is sent to other players, and they don't need the mod.

• Single player (no other human in the game; AI crafts don't count): everything, with solid ships you can land on, shoot, sink and (optionally) lock onto, and attack boats that can fire at you.
• Hosting with other players: the ships, small boats, ferries and moored ships stay (AllowInMultiplayer, on by default), but only you see them, so they're scenery: no collisions, so you never land on or shoot at something the other players can't see. They can't be targeted, damaged or sunk, and attack boats don't fire. Turn AllowInMultiplayer off to clear the sea while others are connected.
• Joining someone else's game: no ships or boats. The harbour lights and the night lights on the game's own moored ships still show, since they're purely local.
• Ship sounds play only where there are ships, so in multiplayer only the host hears them.

SP2 ship models: CarrierLarge, CarrierLarge 1, Destroyer, DestroyerZumwalt, DestroyerWW2, NuclearSub and Yacht.

• Ships are local, so in multiplayer only the host sees them, as scenery (see Multiplayer above).
• The carrier's catapults, arresting wires and elevators don't work, because their scripts are removed. The deck is solid and moves, but the wires won't catch you.
• SP2 has no cargo ship model, so the container ships (and the fallback patrol boat) are simple built-in models.
• Ships anchor about 1.5 km off a harbour rather than entering it. The land/water map is coarse (400 m), so narrow channels aren't used.
• Ships don't avoid each other. Fleets keep their distance when they spawn, but their routes can cross.
• New coastlines are picked up gradually: terrain is sampled a little each frame, and the sea lanes are rebuilt in the background at most every 30 s. Ships may briefly plan around an island's outline box until its terrain has been read.
• Harbours are found by the names of the game's objects and by the shape of what's built at the water's edge. A harbour whose quays are part of the terrain rather than separate objects may get no moored ships. If ships ever moor somewhere odd, the log (with DetailedLog on) shows which quay was used. Rescan Harbours maps everything again.
• Piers narrower than the 8 m map resolution, or T- and L-shaped piers, may get their walkway lamps a little off the middle of the deck or only along part of their length.
• Moored ships stay put; they don't sail off into the sea lanes.
• Small boats only know about land that's loaded near you (with the coarse sea-lane map beyond it). They don't sail under bridges: a bridge deck counts as land.
• Ferries stop at a deep, clear spot off each harbour, as close in as the water allows. They don't come alongside a particular quay. If the harbour isn't loaded yet when the crossing is planned, the terminal is moved in as the ferry approaches. Ferries run only between harbours less than about 28 km apart whose crossing isn't much longer than the straight line.
• Small boats avoid each other and the big ships, but in a tight spot (a busy harbour mouth) two may still pass closer than they should.
• Apart from the motor yacht, the small boats are simple built-in models: SP2 has no other small boat models.
• Lights are glows, not real lights: they don't light up the water or the ships around them.
• Lights fade in at dusk and out at dawn. Seen from above a cloud deck they're dimmed, as the cloud cover would hide them.
• Lighthouse beams stop at land that's loaded (colliders or terrain heightmaps). Over land too far off to be loaded, a beam may reach a little further than it should until that land streams in.
• The lantern's position is read from the lighthouse model: its lantern glass if it has one, otherwise the top of the tower. With DetailedLog on, the log line for each lighthouse says which was used and how high above the sea the lantern is. Lighthouses saved by a pre-release build are dropped from the light cache once and found again as you fly near them.
• Only the main SP2 map is supported.
• Ship sounds are loops played faster or slower for each vessel, not engine simulations. The sounds bypass the game's own mixer: the game's master volume applies, but its effects (cockpit, underwater) are imitated with a low-pass filter.

• SimplePlanes 2 0.7.9
• BepInEx 5 (5.4.x, x64 Mono build) installed in the game folder. On Linux/Steam Deck with Proton, add WINEDLLOVERRIDES="winhttp=n,b" %command% to the game's launch options.

The Gravy Mod Menu is recommended: most mods keep their in-game settings and status there. Without it, edit the .cfg files in BepInEx/config/.