The Golden Gate Bridge is a pretty thing to gaze at, a pain in the butt to paint, and an excellent place to Instagram. But unbeknownst to most of the 40 million annual vehicles often forced to inch across the span, it also sits above a wet and whirring hive of activity, the churning economic engine that helped build the cities that surround it.

Like industrious, capitalist trolls, ships bring about 35 million tons of goods through the Golden Gate every year, on their way to the eight ports of the San Francisco Bay. Wood pulp, nuts, plastic, glass, rubber, electrical machinery: All make their way through these foggy, choppy waters.

Heady and overwhelming stuff for anyone who bothers to really take a look. Fortunately, designer Sam Kronick, who works for the mapping platform Mapbox, has decided to help you visualize how it all goes down. Kronick unearthed a few strange and interesting datasets: One, from the United States Coast Guard, shows the off-shore locations of most (but not all) ships, updated by the minute. A second: The National Oceanic and Atmospheric Administration publishes information of the country’s underwater terrain, the peaks and valleys most don’t see. From there, he reconstructed a day in the life of the San Francisco Bay. Specifically, September 1, 2014. Then he built it all into an animated map.

In the visualization, the lighter purple indicates shallower depths (less than three feet), and the darker, deeper (more than 50 feet). Kronick has extrapolated ships' sizes based on their behavior, with the wide, sandworm-like ones indicating ships longer than 330 feet, the triangles between 330 and 100 feet, and the blippy dots the smallest vessels, at less than 100 feet. Each light green line indicates the path a ship took on the day in question—a more vibrant, Ghostbusters' slime green means a well-worn shipping lane. (Kronick picked the color scheme because it evokes radar, which many ships still use.)

“There’s ton of a little stories in this dataset,” says Kronick. “That’s why I love seeing it play out.”

Watch gigantic vessels retrace identical shipping lanes. See harbor pilots in zippy tugs guide larger ships through the treacherous sand bars at the mouth of the bay. Observe as fishing boats ‘round Half Moon Bay take off in near-union in the morning.

Mapbox

Gaze upon the ghostly tracks of all the ships that fly past Alcatraz Island, or dock at San Francisco’s famous piers.

Mapbox

The project took Kronick a good two weeks, but it was probably worth in the end: The project snagged him a full-time job at Mapbox, where he now hunts for weird datasets full time. And you, incurious landlubber—you keep a better eye on the sea.