Every cell is either water or land. All water cells must be orthogonally connected, and no 2x2 area may be entirely water. Groups of orthogonally-connected land cells form islands, which do not touch orthogonally, but may touch diagonally. Draw a non-intersecting loop through the centres of some cells which passes through each island exactly once. The loop may only visit one cell in each island. If a clue is on a land cell, it indicates the size of its island. Every island must contain exactly one clue. If a clue is on a water cell then the loop must pass through that cell and the clue indicates how many water cells are visited by the loop between the previous island and the next island. Every water section of the loop must pass through exactly one clue. A '?' can represent any non-zero value.