From my Water monotype run in Sapphire
Lombre- Had almost no damaging Grass moves and levels slowly
Tentacool- Levels slow and with a not too good movepool. honestly just had for strength in numbers early on
Goldeen/Seaking- trained for the fight with Tate&Liza into Seaking but ended up being weaker than any other Pokémon on the team
Chinchou- Still training but faints to nearly everything making training more difficult than it should be
Marill- took time to train into Azumarill but was worth it because the Defense Curl/Rollout combo is what saved me against both Norman and Winona