I completed the Phelps Helps set of goals and unlocked the Poseidon fountain finally! Once unlocked, you get ONE of the item for free and then you can buy more of that item for more Gems. This fountain costs 14 Gems if you want more than one.
To see the Phelps Helps set of goals, click here! (This will take you to the first step in the set of goals)
Here is a look at the fountain up close: