Quagsire says hi. Although Gastrodon gets Storm Drain to boost its Sp. Atk, Quagsire has Water Absorb. Quagsire also has the frankly amazing Unaware, allowing it to set up on common stat boosters like Rohbushin and Cloyster. Storm Drain allows Gastrodon to hit quite hard with Special moves though, making it a better Stockpiler than Quagsire. I think Gastrodon is bulkier too. But Unaware alone means Quagsire should also be considered as a Water/Ground.