Seismitoad

Water

• Seismitoad's ability Swift Swim and secondary Ground-typing make it a good Electric-immunity to have on rain teams.
• Swift Swim doubles its Speed in rain, making it one of the fastest Pokemon in the metagame, even outspeeding threats like +1 Volcarona, Tapu Koko, and +1 Mega Charizard X.
• Seismitoad allows for role compression on rain teams as a Stealth Rock user, Swift Swim sweeper, and Tapu Bulu check.
• It is the most viable Stealth Rock user on a rain team, and given its high Speed in rain, it is able to set it up fairly easily.
• It has access to decent coverage options in Sludge Wave and Knock Off.
• Although Seismitoad is quite threatening in rain, it has lackluster Speed and offensive presence outside of rain, and without investment, it isn't able to take hits too well.
• Although it is immune to Electric-type moves, its typing leaves it very weak to Grass-types, which also resist both of its STAB moves.

Ground

Seismitoad's good defensive typing and immunity to Water-type moves make it a good bulky offensive check for threats to Ground in the metagame. The Water immunity granted by Seismitoad's ability Water Absorb gives Ground teams room to maneuver around threats such as Choice Specs Keldeo, and Seismitoad also serves as a hard check to dangerous sweepers such as Belly Drum Azumarill. Modest defenses combined with Assault Vest and a good defensive typing also offer Ground a bulky Ice-neutral Pokemon to switch into threats such as Greninja. Various offensive coverage options allow Seismitoad to threaten Water- and Fairy-types that threaten the team, most notably Azumarill. Access to Knock Off also lets Seismitoad cripple offensive and defensive cores to further support teammates. However, Seismitoad is somewhat passive with mediocre offensive stats and can be easily walled by defensive Pokemon such as Mantine and Zapdos. While fast enough to outspeed most walls, Seismitoad is slower than the majority of offensive threats it is meant to manage and is forced to endure damage whenever checking them. Even with an Assault Vest, Seismitoad is not bulky enough to switch into powerful special wallbreakers such as Latios consistently. A lack of reliable recovery also means Seismitoad can be difficult to keep healthy over a battle. Seismitoad also competes with Gastrodon as a Water-immune Pokemon on Ground, which has better defenses and reliable recovery to consistently check threats such as Keldeo and Greninja. However, Seismitoad is able to check Azumarill, which Gastrodon can't.