Blastoise, Starmie and Gyrados!
Gyarados
Blastoise is the best but gyarados and cloyster are also very strong
The best water type would be Kyogre but you can't get it in leafgreen you need to get one from sapphire or emerald other than that the best water Pokemon is blastoise.
dragonite is the strongest dragon there is in leafgreen
Manaphy is a legendary water type of Pokemon. It is not possible to get this Pokemon in the game Pokemon LeafGreen.
I think its moltres
I guess Zapdos
the best Pokemon are mewto and the rarest Pokemon ever mew.
pikapoo
you can catch water Pokemon by surfing on water and by using all the rods
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MunchingOrange