How do you get underwater rooms on webkinz?

You must buy an underwater pet (fish, manatee, seahorse...) and adopt it onto your account. If you have 10 pets or less, you get it automatically when you go to your room. If you have more than 10 pets on the account, go to My Room, then click Map. Select Buy, then buy the underwater room (it is blue, 10X10 and costs 1000 KC).