Hey doesn't sun kinda ruin Gastrodon's water attacks?
Yes but Gastrodon runs more of a bulky water/support role on this team storm drain attracts all water move other then surf to Gastrodon and give it a water immunity and a +1 s.atk boost this is good for both doubles and singles. Other then that it move pool contains.i You could also run it on a rain team to abuse Volcarno's hurricane and add in hidden power water to get a psuedo stab.
It's support moves include Toxic, subsititute, protect, yawn, and rain dance
It's special move pool includes Ice beam, surf, scald, sludge bomb, sludge wave, and earth power(you need to get it from 4th gen for this move)
Physical sets can have Earthquake, stone edge, rock slide, waterfall, body slam, and curse but these work better with sand strength
Gimicky/specialized moves include clear smog, mist, stockpile, swallow, spit up, mirror coat, and counter (pain split, sleep talk, and endure are 4th gen move tutors)
It adds water and ground stab to hit targets Volcarno can't deal good damage on specificlly water and rock types although ice beam also handles dragon types.