Nurikabe Instructions

Rules: The objective is to divide the grid into shaded and unshaded cells, subject to the following rules:

1. Each numbered cell is an island cell, the number in it is the number of cells in that island.
2. Each island contains exactly one numbered cell.
3. There must be only one stream, which is not allowed to contain "pools", i.e. 2x2 areas of shaded cells.