The salmon swim upstream against the current to spawn.
Tips
usage
Common in 洄游 — the biology term for fish migration (salmon, eels) swimming back upstream against the current. The base image is water turning back on itself in a whirl.
Three-drop water radical, side-form of 水. It fixes the meaning on moving water — here water curling back into an eddy. Same family as 流 to flow, 漩 whirlpool, 波 wave.
Right side 回 gives both the sound huí and the meaning: a swirl is water 'returning,' turning back on itself. The nested-square shape itself pictures something spiraling inward.