This is a typical North American currents station. You can see the times of the slacks, the floods, and the ebbs. The direction of the currents are given in true degrees (due north is 0°). The time to the next event is listed at the bottom.

When you rotate the iPhone, the currents graph appears. Areas above zero are flood currents, and areas below are ebb currents.

Dragging your finger across the graph will show you the value at that point, indicated by the target circle.