seam
The visible boundary where fast current meets slow current — a line on the water's surface where two different speeds of flow run side by side. Fish position themselves on the slow side of a seam and dart into the fast side to intercept food. For anglers, seams are the most consistently productive water on any river.
Etymology
Old English sēam, a joining or junction. The same word used for the stitched junction of two pieces of fabric. On a river, the seam is where two fabrics of current are sewn together.
Notes
Paddlers also use this term — what anglers call a seam, kayakers call an <a href="https://rewilding.mx/word/eddy-line/" class="word-autolink">eddy line. Same feature, different purpose.
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