fish swimming, fishing with a net
汕 centers on fish moving through water, specifically the act of swimming or being caught in a net. The two given meanings are connected by the image of fish in motion within a body of water.
汕 combines 氵 (water) with 山 (mountain), but the exact historical development is uncertain. The character is rare, and the component relationship may be phonetic rather than semantic.
Water 氵 beside a mountain 山: picture fish swimming in a mountain stream, or a net being cast into the water near the mountain's edge.
For サン, imagine the sun (サン) sparkling on the water as fish swim and nets are cast: sun -> サン, and the mountain stream glitters with light.
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