Logic Masters Deutschland e.V.

• Normal sudoku: Fill every row, column and marked 3×3 box with the digits 1 to 9 once each.
• River & riverbank: Locate a river (think: classic snake) in the grid, consisting of a one-cell wide, non-looping, non-branching string of orthogonally connected cells, which may not touch itself orthogonally (but may diagonally); each border between a river cell and a non-river cell is a riverbank segment (this precludes the grid edge from being counted as riverbank).
• Riverbank sweeper: Each circled cell is a riverbank sweeper, which counts riverbank segments within the (up to 3×3) surrounding cells (see example image - but ignore the squared sentinel which is irrelevant for this puzzle).
• German whispers: Neighboring cells along the river differ by 5 or more.
• No negative constraint: Not all circles are necessarily given.

To familiarize yourself with the riverbank ruleset, please consider first taking a look at the 6×6 introductory puzzle Episode 2: Adobe Illustrator.

• Download this puzzle as: scalable image (SVG) | bitmap image (PNG) | printable document (PDF).
  Note: SVG auto-switches colors depending on light/dark mode in system/browser setting; PDF is in printing-friendly black on white.
• Play online on: Penpa+ | CtC App.

The riverbank ruleset is based on Borderline by @Jakhob & @wooferzfg.