Normal sudoku rules apply. Each cell in the grid belongs to exactly one terrain: Either island (green) or water (blue). All water cells in the grid must form one orthogonally connected region. Each 2x2 region in the grid contains at least one cell from each terrain. Each island contains exactly one clue, which equals the product of the size of the island (i.e. the number of cells that belong to this island) and the sum of the digits in all cells belonging to this island. Digits within an island do not repeat. Islands are not allowed to touch each other (neither orthogonally nor diagonally). A digit in a circle equals the size of the island. Not all possible circles are given.