The Water Gem is a magical crystal that contains great power, which can be used to summon and control the Sapphire Fairycorn if united with the Air Gem and Earth Gem by the Vase of the Three Realms.
Barbie: A Touch of Magic[]
The water gem was hidden in a sunken ship by a pirate queen, which ended up in a cave in Pacifica before Brooklyn found it.
Skipper once accidentally wished her parents to turn into babies. Because it was done by a magical gem, the only way to reverse was with a counter-spell using the Earth Gem. Skipper made a wish to be more responsible and think from their perspective while holding the Earth Gem. The wish successfully turned her parents back into adults.
It was later stolen by Dru Charles, who used all the gems to control the Sapphire Fairycorn, make herself famous and steal magic from all three realms until Malibu tricked her into destroying the magic. The gems all broke to pieces as a result.