Swampy Mystery Ducks are the main variant of the Mystery Duck which appear in Mystery Duck Challenges.
- Swampy Mystery Ducks are found in some Mystery Duck challenges. A new Mystery Duck challenge appears every 24 hours, but a different type of Mystery Duck will likely feature.
- When a player collects a Swampy Mystery Duck and completes the challenge, it is added to the Mystery Duck counter. For every three Mystery Ducks collected, a new Duckie costume is unlocked.
- Swampy Mystery Ducks require five drops of Water to fill and collect. All other Fluids, except Steam will kill Swampy Mystery Ducks. If the Swampy Mystery Duck is killed or if the level is completed without it being collected, the level fails.
- Once all Duckies that are unlocked with the Mystery Duck are unlocked, Mystery Duck challenges will no longer appear, thus, neither will the Swampy Mystery Duck.
- While Full, the Swampy Mystery Duck takes on the appearance of a full Swampy Duck with a red, black and white tuxedo, a slightly slimmer body and has his top eye lid down. He wears a top hat with a red ribbon.
- While Empty, the Swampy Mystery Duck takes on the appearance of an empty Swampy Duck with a tuxedo in various shades of orange. His hat remains the same.