A trawler is a fishing boat that drags a large net, called a trawl, through the water to catch fish. The net looks like a giant sock or funnel, wide at the opening and narrow at the end, scooping up everything in its path as the boat pulls it along the ocean floor or through deeper water.

Trawlers revolutionized commercial fishing in the late 1800s. Before trawlers, fishermen used hooks, lines, and smaller nets from rowboats or sailing vessels, catching only what they could reach by hand. Modern trawlers can stay at sea for weeks, using powerful engines and refrigeration to bring back huge catches. Some trawlers are enormous ships with crews of dozens, processing and freezing fish right on board.

When you trawl through old photos looking for a specific picture, you're searching methodically through everything, just like a trawler's net sweeps through the water. While trawling made it possible to feed millions of people with affordable fish, it can also catch unwanted sea creatures and disturb the ocean floor, which is why fishing rules limit where and how trawlers can operate.