The Great Marsh is located in Pastoria City in Sinnoh, and has many Pokémon that can not be found anywhere else in Sinnoh. It costs 
500 to enter, and you will receive 30 Safari Balls to catch Pokémon, but you can only go 500 steps before your time is over, though you can retire anytime. You are also not allowed to save here. The great marsh has 6 different areas in it, and each one of them has certain Pokémon in them, their locations changing every day. You can see random Pokémon and their locations through the binoculars on top of the marsh's entrance building at the cost of 100. In Diamond and Pearl, a boy with green hair at the start of the great marsh will give you HM05 Defog, and will give you Shards in Platinum. In Platinum, there is also a girl at the entrance of the building who will give you a challenge to find and catch 5 Pokémon, rewarding you with the Matchup Checker Pokétch App.
Pokémon
| Name | Sprite | Level | How |
|---|---|---|---|
| Arbok |  |
24-30(D/P) 30(Plt) | Grass (After getting the National Dex-FireRed cartridge needed) |
| Paras |  |
20-26 | Grass (After getting the National Dex) |
| Psyduck |  |
20-40 | Grass/Surf (Diamond/Pearl only) |
| Golduck |  |
20-26 | Grass/Surf (Diamond/Pearl only) |
| Exeggcute |  |
20-26 | Grass (After getting the National Dex) |
| Kangaskhan* |  |
20-26 | Grass (After getting the National Dex) |
| Tangela |  |
27-31 | Grass (Platinum only) |
| Magikarp |  |
3-25 | Old Rod/Good Rod |
| Gyarados |  |
15-55 | Good Rod/Super Rod |
| Marill |  |
20-30 | Grass/Surf (Diamond/Pearl only) |
| Hoothoot |  |
20-24(D/P) 26-27(Plt) | Grass (Night) |
| Noctowl |  |
26(D/P) 28-30(Plt) | Grass (Night) |
| Yanma |  |
20-26(D/P) 26-31(Plt) | Grass (After getting the National Dex-D/P only) |
| Wooper |  |
20-30(D/P) 26-40(Plt) | Grass/Surf |
| Quagsire |  |
20-40 | Grass/Surf |
| Shroomish |  |
20-26 | Grass (After getting the National Dex) |
| Azurill |  |
20-24 | Grass (Diamond/Pearl only) |
| Roselia |  |
20-26 | Grass |
| Gulpin |  |
20-26 | Grass (After getting the National Dex) |
| Carvanha |  |
15-30(D/P) 30-55(Plt) | Super Rod (After getting the National Dex) |
| Barboach |  |
15-20(D/P) 10-25(Plt) | Good Rod |
| Whiscash |  |
30-55(D/P) 20-50(Plt) | Super Rod |
| Kecleon |  |
20-26 | Grass (Platinum only) (After getting the National Dex) |
| Tropius |  |
28-30 | Grass (Platinum only) |
| Starly |  |
22-26 | Grass (Diamond/Pearl only) (Day & Morning) |
| Staravia |  |
20-26 | Grass |
| Bidoof |  |
22-26 | Grass (Diamond/Pearl only) |
| Bibarel |  |
21-25(D/P) 26-28(Plt) | Grass |
| Budew |  |
20-26 | Grass (Diamond/Pearl only) (Day & Morning) |
| Skorupi |  |
20-26 | Grass |
| Drapion |  |
20-26 | Grass (After getting the National Dex) |
| Croagunk |  |
20-26 | Grass |
| Toxicroak |  |
20-26 | Grass (After getting the National Dex) |
| Carnivine |  |
20-26 | Grass |
Note 1:Pokémon whose names are in bold change between themselves daily.
Note 2:Yanma is a daily Pokémon only in Pokémon Diamond and Pearl.
| Characters · Pokédex | |||||||
| Settlements | |||||||
| Pokémon League | |||||||
| Routes | |||||||
| Islands | |||||||
| Caves, Tunnels and Mountains | |||||||
| Lakes | |||||||
| Battle Zone |
| ||||||
| See also | |||||||
| Regions | |||||||