A river (강, gang) is read as the flow and direction of your life more than any single event — a moving, continuous symbol rather than a static one, which sets it apart from most of the other entries in this category.
A calm, clear river flowing steadily is read as life proceeding smoothly in whatever direction you're currently headed — one of the more quietly reassuring water dreams available. A rough, fast-moving, or turbulent river shifts the reading toward a period that feels harder to navigate, though generally still moving forward rather than stuck.
Crossing a river is treated as one of the more significant single actions in this whole tradition, echoing a near-universal idea across many cultures — including Korea's own folk image of a river separating this life from the next — of a river marking a real turning point or major decision. Successfully crossing is read as committing to and completing a big transition; struggling partway across is read as being caught mid-decision.
A river running dry is read as stagnation — momentum or resources that have stopped flowing, worth taking as a nudge to actively get things moving again rather than waiting for the water to return on its own. Swimming with the current versus against it maps fairly literally onto going along with your circumstances versus resisting them.