Water naturally flows downhill — avoiding the high ground and seeking the low. An army naturally avoids strength and strikes weakness. To swim against the current is not water's nature.
And yet, salmon do it. They leap up waterfalls, fight the rushing stream, and return to the place where they were born. The phrase "逆流而上" (swimming against the current) became an idiom for those who go against the prevailing trend — who choose the harder path because it is the right one.
水之行，避高而趋下；兵之形，避实而击虚。逆流而上者，非水之性也。
水之行，避高而趋下；兵之形，避实而击虚。逆流而上者，非水之性也。
Reflection & Analysis · 寓意解读
Core Wisdom
The current is comfortable. The current is easy. The current takes you where everyone else is going. The one who swims against it is either a fool — or a salmon.
This idiom draws on both military strategy and natural observation. In war, going against the natural flow is usually disastrous. But in character, going against the social flow — refusing to follow the crowd, resisting peer pressure, maintaining principles when everyone else abandons them — is the mark of true courage.
The salmon metaphor adds depth: the salmon does not swim against the current for sport. It does so because its purpose demands it. The one who goes against the tide must have a reason strong enough to justify the struggle.