BLUB! This place is Underwater! Just look at all the colorful fish... ...and unusual plant life! Don’t stay too long... ...or you’ll get pruned.
Underwater was an aquatic place located on the seafloor of Club Penguin. It could be accessed from a door in the Hidden Lake. However, the door was locked, and required players to enter it via a different route, by playing Puffle Rescue. Once inside, players could obtain the Moss Key Pin, and keep the door open.
This underwater room had various sunken treasure, and contained many types of corals, seashells, and other forms of aquatic life. Jellyfish and Fluffies were a common sight here.
This room was first accessible during the Cave Expedition. Initially, no key was required to enter. The Coral Reef Background could be obtained for free here. After cave-ins at the Cave Mine, this room was no longer accessible due to the Cave Mine and Hidden Lake being sealed off. After the cave-in was cleared, this room was accessible again, although it has since required players to play through Puffle Rescue, and then obtain the Moss Key Pin.
Originally, only members could enter this room, due to the level of Puffle Rescue that it must be accessed from can only be played by members. Even if a player owned the Moss Key Pin but their membership later expired, they could no longer enter. However, as of April 10, 2014, if a member obtained the pin, but their membership later expired, they would still be able to enter this room.
If you threw a snowball, here, it would turn into a bubble, and popped upon impact.
During the Holiday Party 2013, members with trains were able to bring non-members here, and if the non-member exited the train, they could stay in the room. Shortly after, this trick was fixed, meaning that if a member with a train brought the non-members to the room, the non-members would automatically be kicked out of the train by a key note and stay at the Hidden Lake, resulting in only member penguins, who obtained the key, staying in the Underwater room.