Nurikabe Knights

Normal sudoku rules apply.

Divide the grid into a number of islands -- orthogonally connected groups of cells. Every island contains a single circled cell; the digit in the circle indicates the number of cells making up the island.

The islands are surrounded by a waterway -- a single orthogonally connected group of cells. All caged cells are waterway cells; the digit in a caged cell indicates how many waterway cells are seen orthogonally from that position, including itself (island cells block vision). The waterway cannot form any 2x2 areas.

Cells a chess knight's move apart cannot contain the same digit.