You might be thinking of a similar Pokemon called Starmie, which can be caught in Pokemon XD: Gale of Darkness. It's found in the following locations:
* Route 206: This is the most common place to find Starmie.
* Route 208: You have a smaller chance of encountering Starmie here.
Starmie is a Water/Psychic type Pokemon with high Special Attack and Speed stats. It's a powerful Pokemon, so if you're looking for a strong Water type, Starmie is a great option!