w-sound problem

When I pronounce English words, I have a problem with "w-sound" such as wolf, world, wood... Long time ago, an English teacher told me "Be a fish!". I practiced over and over, but w-sound was still difficult for me. Today, I unexpectedly found a list of the same sound words in my daughter's notebook. The list said, "would" and "wood" in the same sound. I thought it was wrong. Then I looked up those words in the dictionary, and recognized those are the same sound words. I could pronounce "would" without any problems. Now I would pronounce "wood" without any problems either.