Muddy Water is learned by 21 species by level, 99 by machine and 17 by egg

Effect, in PokéAPI's words

“Has a chance to lower the target’s accuracy by one stage.”

Who learns it

100 species in all, 8 of 17 games shown

Scarlet and Violet: 75 species

Species	Method	Level
Kyogre	Level up, Machine	27
Wooper	Level up, Machine	28
Barboach	Level up, Machine	31
Shellos	Level up, Machine	31
Whiscash	Level up, Machine	33
Gastrodon	Level up, Machine	33
Quagsire	Level up, Machine	34
Tatsugiri	Level up, Machine	39
Vaporeon	Level up, Machine	40
Marshtomp	Level up, Machine	40
Swampert	Level up, Machine	42
Clauncher	Level up, Machine	50
Goomy	Level up, Machine	50
Clawitzer	Level up, Machine	56
Sliggoo	Level up, Machine	56
Goodra	Level up, Machine	58
Squirtle	Machine
Wartortle	Machine
Blastoise	Machine
Psyduck	Machine
Golduck	Machine
Poliwag	Machine, Egg
Poliwhirl	Machine, Egg
Poliwrath	Machine, Egg
Tentacool	Machine
Tentacruel	Machine
Slowbro	Machine
Seel	Machine
Dewgong	Machine
Horsea	Machine
Seadra	Machine
Gyarados	Machine
Lapras	Machine
Mew	Machine
Totodile	Machine
Croconaw	Machine
Feraligatr	Machine
Chinchou	Machine
Lanturn	Machine
Marill	Machine
Azumarill	Machine
Politoed	Machine, Egg
Slowking	Machine
Kingdra	Machine
Tyranitar	Machine
Mudkip	Machine
Lotad	Machine
Lombre	Machine
Ludicolo	Machine
Wingull	Machine
Pelipper	Machine
Corphish	Machine
Crawdaunt	Machine
Feebas	Machine
Milotic	Machine
Floatzel	Machine
Hippopotas	Machine
Hippowdon	Machine
Basculin	Machine
Keldeo	Machine
Skrelp	Machine
Dragalge	Machine
Mareanie	Machine
Toxapex	Machine
Sobble	Machine
Drizzile	Machine
Inteleon	Machine
Drednaw	Machine
Pincurchin	Machine
Basculegion	Machine
Tadbulb	Machine, Egg
Bellibolt	Machine
Wiglett	Machine
Wugtrio	Machine
Clodsire	Machine

Brilliant Diamond and Shining Pearl: 19 species

Species	Method	Level
Kyogre	Level up	27
Wooper	Level up	28
Barboach	Level up, Egg	31
Shellos	Level up	31
Whiscash	Level up	33
Gastrodon	Level up	33
Quagsire	Level up	34
Vaporeon	Level up	40
Marshtomp	Level up	40
Swampert	Level up	42
Squirtle	Egg
Tentacool	Egg
Lickitung	Egg
Horsea	Egg
Omanyte	Egg
Marill	Egg
Azurill	Egg
Clamperl	Egg
Relicanth	Egg

Sword and Shield: 76 species

Species	Method	Level
Kyogre	Level up, Machine	27
Wooper	Level up, Machine	28
Barboach	Level up, Machine	31
Shellos	Level up, Machine	31
Whiscash	Level up, Machine	33
Gastrodon	Level up, Machine	33
Quagsire	Level up, Machine	34
Vaporeon	Level up, Machine	40
Marshtomp	Level up, Machine	40
Tympole	Level up, Machine	40
Stunfisk	Level up, Machine	40
Swampert	Level up, Machine	42
Tapu Fini	Level up, Machine	45
Palpitoad	Level up, Machine	48
Clauncher	Level up, Machine	50
Goomy	Level up, Machine	50
Seismitoad	Level up, Machine	54
Clawitzer	Level up, Machine	56
Sliggoo	Level up, Machine	56
Goodra	Level up, Machine	58
Squirtle	Machine
Wartortle	Machine
Blastoise	Machine
Golduck	Machine
Poliwag	Machine
Poliwhirl	Machine
Poliwrath	Machine
Tentacool	Machine
Tentacruel	Machine
Slowbro	Machine
Lickitung	Machine
Horsea	Machine
Seadra	Machine
Goldeen	Machine
Seaking	Machine
Gyarados	Machine
Omanyte	Machine
Omastar	Machine
Mew	Machine
Marill	Machine
Azumarill	Machine
Politoed	Machine
Slowking	Machine
Kingdra	Machine
Larvitar	Machine
Pupitar	Machine
Tyranitar	Machine
Lombre	Machine
Ludicolo	Machine
Azurill	Machine
Corphish	Machine
Crawdaunt	Machine
Feebas	Machine
Milotic	Machine
Relicanth	Machine
Hippopotas	Machine
Hippowdon	Machine
Lickilicky	Machine
Basculin	Machine
Tirtouga	Machine
Carracosta	Machine
Jellicent	Machine
Keldeo	Machine
Barbaracle	Machine
Wishiwashi	Machine
Mareanie	Machine
Toxapex	Machine
Golisopod	Machine
Dhelmise	Machine
Sobble	Machine
Drizzile	Machine
Inteleon	Machine
Drednaw	Machine
Clobbopus	Machine
Grapploct	Machine
Pincurchin	Machine

Ultra Sun and Ultra Moon: 31 species

Species	Method	Level
Tympole	Level up	27
Palpitoad	Level up	28
Seismitoad	Level up	28
Barboach	Level up, Egg	35
Vaporeon	Level up	37
Shellos	Level up	37
Marshtomp	Level up	38
Goomy	Level up	38
Sliggoo	Level up	38
Goodra	Level up	38
Swampert	Level up	39
Whiscash	Level up	39
Stunfisk	Level up	40
Gastrodon	Level up	41
Wooper	Level up	47
Clauncher	Level up	48
Tapu Fini	Level up	48
Quagsire	Level up	53
Clawitzer	Level up	57
Kyogre	Level up	60
Squirtle	Egg
Tentacool	Egg
Lickitung	Egg
Horsea	Egg
Omanyte	Egg
Marill	Egg
Azurill	Egg
Clamperl	Egg
Relicanth	Egg
Basculin	Egg
Wishiwashi	Egg

Sun and Moon: 31 species

Species	Method	Level
Tympole	Level up	27
Palpitoad	Level up	28
Seismitoad	Level up	28
Barboach	Level up, Egg	35
Vaporeon	Level up	37
Shellos	Level up	37
Marshtomp	Level up	38
Goomy	Level up	38
Sliggoo	Level up	38
Goodra	Level up	38
Swampert	Level up	39
Whiscash	Level up	39
Stunfisk	Level up	40
Gastrodon	Level up	41
Wooper	Level up	47
Clauncher	Level up	48
Tapu Fini	Level up	48
Quagsire	Level up	53
Clawitzer	Level up	57
Kyogre	Level up	60
Squirtle	Egg
Tentacool	Egg
Lickitung	Egg
Horsea	Egg
Omanyte	Egg
Marill	Egg
Azurill	Egg
Clamperl	Egg
Relicanth	Egg
Basculin	Egg
Wishiwashi	Egg

Omega Ruby and Alpha Sapphire: 29 species

Species	Method	Level
Tympole	Level up	27
Palpitoad	Level up	28
Seismitoad	Level up	28
Barboach	Level up, Egg	35
Vaporeon	Level up	37
Shellos	Level up	37
Marshtomp	Level up	38
Goomy	Level up	38
Sliggoo	Level up	38
Goodra	Level up	38
Swampert	Level up	39
Whiscash	Level up	39
Stunfisk	Level up	40
Gastrodon	Level up	41
Wooper	Level up	47
Clauncher	Level up	48
Quagsire	Level up	53
Clawitzer	Level up	53
Kyogre	Level up	60
Squirtle	Egg
Tentacool	Egg
Lickitung	Egg
Horsea	Egg
Omanyte	Egg
Marill	Egg
Azurill	Egg
Clamperl	Egg
Relicanth	Egg
Basculin	Egg

X and Y: 28 species

Species	Method	Level
Kyogre	Level up	20
Tympole	Level up	27
Palpitoad	Level up	28
Seismitoad	Level up	28
Vaporeon	Level up	37
Marshtomp	Level up	37
Shellos	Level up	37
Goomy	Level up	38
Sliggoo	Level up	38
Goodra	Level up	38
Swampert	Level up	39
Stunfisk	Level up	40
Gastrodon	Level up	41
Wooper	Level up	47
Clauncher	Level up	48
Quagsire	Level up	53
Clawitzer	Level up	53
Squirtle	Egg
Tentacool	Egg
Lickitung	Egg
Horsea	Egg
Omanyte	Egg
Marill	Egg
Azurill	Egg
Barboach	Egg
Clamperl	Egg
Relicanth	Egg
Basculin	Egg

Black 2 and White 2: 23 species

Species	Method	Level
Kyogre	Level up	20
Tympole	Level up	27
Palpitoad	Level up	28
Seismitoad	Level up	28
Vaporeon	Level up	37
Marshtomp	Level up	37
Shellos	Level up	37
Swampert	Level up	39
Stunfisk	Level up	40
Gastrodon	Level up	41
Wooper	Level up	47
Quagsire	Level up	53
Squirtle	Egg
Tentacool	Egg
Lickitung	Egg
Horsea	Egg
Omanyte	Egg
Marill	Egg
Azurill	Egg
Barboach	Egg
Clamperl	Egg
Relicanth	Egg
Basculin	Egg

Changed over time

One change since Generation III

1. Through Gen VPower 9590 from X and Y, Generation VI