Instructions
Install the DesignByMe program. Click the download button on LEGO's website, http://designbyme.lego.com/en-us/default.aspx. Double-click the file that is downloaded to your computer and read the instructions to download the DesignByMe program.
Open DesignByMe. Click the "Start" button, click "All Programs" and click "DesignByMe."
Click on the style of blocks that you want to use for your lake monster. Many famous sea monsters have large, round stomachs, so you may want to start there.
Click on the color that you want to make the blocks. Lake monsters are commonly portrayed as being earth tones such as brown and dark green.
Connect the blocks in the center of the screen.
Click "Upload" to send the design to LEGO. Click the "Check Price" option to see how much it would cost for the actual LEGO lake monster. Buy the LEGO lake monster within this screen. When the design is purchased, the pieces with proper instructions are sent to you.