Well, let's take a look.
As with previous Safari Zones, Pokémon are made easier and harder to catch by modifying their catch rates. An escape rate is also given for each Pokémon that appear in the Great Marsh. The escape rates for Pokémon are the same for all Generation IV games, except that those who do not appear in the Great Marsh or the Johto Safari Zone do not have their escape rates defined in the relevant games.
At the start of an encounter, both rates are set to their species defaults. Throwing Bait will lower the escape rate by one stage, but will also have a 90% chance of lowering the catch rate by one stage. Conversely, throwing Mud will raise the catch rate by one stage, but will also have a 90% chance of raising the escape rate by one stage. Stages for catch rates and escape rates work identically to stat stages: they may not be raised above +6 or below -6, where 0 is the starting stage. The stage multipliers applied to the catch rates and escape rates are also identical to that of stat stages.
At the end of each turn, a random number between 0 and 255 is generated, and if it is less than the modified stat stage, the Pokémon escapes.
Your BEST shot would be to throw mud then immediately use a Safari Ball.