Gastrodon

Ground

Thanks to its ability Storm Drain, Gastrodon is one of the two viable Ground-types that are immune to Water-type moves, making it a key partner on Ground teams. Its secondary Water typing gives it an important neutrality to Ice-type moves and lets it wall certain foes like non-Choice Band Mamoswine, and its decent natural bulk enables it to tank even the strongest moves of the metagame, such as Choice Band Diggersby's Return. In addition to its typing and bulk, reliable recovery in the form of Recover enables Gastrodon to continually switch into threatening Pokemon like Greninja and Keldeo. However, Gastrodon's typing also leaves it virtually defenseless against problematic Grass-types, such as Mega Venusaur and Ferrothorn, and Pokemon like Volcarona and Alolan Raichu that often carry Grass-type coverage moves. Moreover, Gastrodon has an abysmal Speed stat coupled with a low Special Attack stat, making it prone to losing momentum and susceptible to Taunt from stallbreakers like Mew and Hydreigon. Finally, Gastrodon fights with Seismitoad for a spot on any Ground team as the Water-immune Pokemon, as the latter possesses a superior offensive presence and is able to check Azumarill, one of the greatest threat to Ground teams. On the other hand, Gastrodon's superior longevity thanks to Recover helps it check dangerous foes consistently, which Seismitoad cannot do.

Water

Gastrodon is the only Electric-immune Pokemon Water has access to that also has reliable recovery, making it a very solid option on any balanced Water team. Gastrodon finds its niche on Water-type teams by being able to switch into Trick users such as Latios because of Sticky Hold while also being able to wall Pokemon such as Mega Diancie. Since Gastrodon is only weak to Grass, it is often hard for teams that lack Grass-type coverage to find ways to revenge kill it. It does, however, stack Water teams' natural weakness to Grass-type coverage. Gastrodon's low Speed and passive nature also leave it vulnerable to Taunt from stallbreakers like Mew and Gliscor preventing it from recovering off damage and acting as a wall. Gastrodon does not appreciate being badly poisoned, as it severely limits Gastrodon's ability to effectively wall Pokemon like Mega Diancie. Furthermore, Gastrodon faces competition from Mega Swampert as a team's Electric switch-in; Swampert has the ability to set Stealth Rock, but Gastrodon is a reliable wall and can more easily switch into Electric-type Pokemon lacking Grass-type coverage due to Recover.