Instructions
Navigate to the Webkinz website and log into your account. To get an underwater room you must have a swimming type Webkinz plush toy like a fish, dolphin, seahorse, shark or crab.
Click the "Things to Do" tab at the bottom of the screen and click the "Adoption Center" option from the list that appears.
Enter a name and gender for the swimming type pet and then click "OK." Check the tag attached to your Webkinz toy for the secret code and type it into the screen that is shown before clicking "Next." Your swimming pet will then be placed inside its new underwater room.
Click on the "My Stuff" tab at the bottom of the screen to show a list of decorations and furniture that you have available. To add new things to this list click on the "W Shop" icon and buy new decorations using your "Kinzcash." You can earn this virtual currency for the game by playing the mini-games in the arcade area or doing jobs.
Click on the decoration displayed under the "My Stuff" tab and drag it into the room to place it. The underwater room can hold normal decorations as well as the special underwater ones that cannot be place in other rooms. Do not make your underwater rooms too cluttered and keep to a theme to avoid making it look jumbled.