the pool is a L shaped....

_________L_______
| 2 |
|_________ | W
| 1 |
|________|

If you extend the vertical line between sections 1 and 2, it would separate the shallow end from the deep end and in essence create two rectangles. Rectangle 1 representing the shallow end and rectangle 2 representing the deep end. The diving board is along the left vertical lines

rectangle 1 - 21 x 22 x 3 (LXWXD)
rectangle 2 - 20 X 18 X 8 (starts at 6' ends at 8' deep) the 6' section (more or less) runs along the vertical line between rectangle 1 and 2