I have just enough tutorials now to release the main site of my tileset tutorials.
Lession 3 makes use of the Lakebed tiles, located at the bottom of the tileset.
(http://solarus_resource.site88.net/tutorial/01/lakebed/lakebed.gif)
http://solarus_resource.site88.net/tutorial/index.htm
Go and check it out :)
Happy mapping!