Again, strategy.
http://pokemondb.net/pokebase/47910/what-pokemon-have-a-double-resistance-to-water
Pleaselog inorregisterto add a comment.
Kingdra, Palkia, Corsola, Omanyte, Omastar, Kabuto, Kabutops, Tirtouga, Carracosta, Magcargo, Reshiram, and Relicanth. As you can see most are water types. It is worth noting thatall Pokemon with Flash-fireare immune to Fire.
Fire-Rock pokemon that have a 2x resistance:
Magcargo
Fire-Dragon pokemon that have a 2x resistance:
Reshiram
Water-Rock pokemon that have a 2x resistance:
OmanyteOmastarKabutoKabutopsCorsolaRelicanthTirtougaCarracosta
Water-Dragon pokemon that have a 2x resistance:
KingdraPalkia
Sources: Pokemon Database and Serebii