Oh no, Gastrodon West Sea and East Sea forms found each other! You know they are serious when they actually lift their bodies off the ground on their parapodia- hommies gunna slug it out; someone going to a pokemon center before this is finished.

Gastrodon is one of my most favorite pokemon ever- not very strong but VERY durable, and it only has 1 weakness.
-Recover
-Mud Bomb(lower accuracy STAB)
-Scald(Burn to nuke STR and chip damage)
-Yawn(knock em out)
-OR Stockpile(Raise Sdef&Def up to 3 times). Stockpile and Yawn are egg moves; gotta breed it into Gastrodon, it won't learn it naturally.

Wanna know my favorite Duos teams? Typhlosion(OG, not Hisuian) & Gastrodon. Gastrodon only has one weakness, but its 4x- hit it with Grass and it is done. But... are you sure you want to send a grass type with Typhlosion standing there? Oh okay, so wipe out Typhlosion first... Water Absorb on Gastrodon; if they try to use a multi-target water attack(which they generally do in Duos) you will power up Gastrodon. Also, Typhlosion is one of my favorite pokemon, but I chose the OG one specifically for a good reason. Burn Up. Extremely strong Fire type attack... that removes the Fire typing of the pokemon. OG Typhlosion is only Fire type, so by removing that you have created a NULL TYPE pokemon. He has NO WEAKNESSES. You can't hit him for super effective damage, and he will guard Gastrodon's only weakness.