diff --git a/README.md b/README.md
index 7dfb450..e584579 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,7 @@ go get -u github.com/songgao/water/waterutil
 
 ## Documentation
 [http://godoc.org/github.com/songgao/water](http://godoc.org/github.com/songgao/water)
+[http://godoc.org/github.com/songgao/water/waterutil](http://godoc.org/github.com/songgao/water/waterutil)
 
 ## Example