MASTCHAIN is a big group of people who help watch the ships on the ocean.

Ships send little radio messages that tell where they are. These messages are called AIS. To hear them, you place a small receiver near the water, and it picks up the signals from passing ships.

All these receivers talk to one big system that puts the messages together. This lets everyone see where ships are moving around the world.

MASTCHAIN is useful because:

• It helps make the ocean safer, since people can see where ships are. • It helps ports know when ships will arrive. • It helps scientists learn how ships move and how they affect the environment. • It helps many groups understand what is happening on the ocean in real time.

And the best part. People who run a receiver get rewarded for helping the network grow. You help the world understand the ocean, and you earn something in return.