Nurikabe Pentominoes Instuctions

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

1. Each lettered cell is an island cell, the letter in it indicates the pentomino it is part of (tetrominoes used in the example below).
2. Each island contains exactly one lettered cell.
3. There must be only one stream, which is not allowed to contain "pools", i.e. 2x2 areas of shaded cells.