Green Water

Seven kinds of ship, any sea you like. Where does each one hit its limit?

1. Pick a ship on the Ship tab, from a harbour tug to a 330 m container ship, and set her engine and course.
2. Set the sea on the Sea tab: a wind sea and a swell, each with its height, period and direction. Or start from a preset.
3. Watch the limits. Seven bars show how close she is to slamming, shipping green water over the bow, lurching too hard, rolling too far, or going into parametric roll. The line on each bar is the limit.
4. Headings shows every course at once, so you can see which way to steer. Classes shows the wave height each kind of ship can take in this sea.
5. Passage is the challenge: get your ship across to port by her ETA with a storm crossing the route. Drag the waypoints, scrub the forecast, ease the engine or heave to.

Period matters as much as height. A long ship rides short waves that throw a tug about, and a swell whose length matches hers can do what a bigger sea can't. Drag the sea to look around; pinch or scroll to zoom.

Alongside