They appear in the series during the episodes where Sam and Tucker use underwater gear , but the reliable episode index I found does not identify a single “underwater mission” title from the show’s full 53-episode list.

What can be confirmed

  • Danny Phantom ran for 3 seasons and 53 episodes.
  • The episode list shows the series aired from April 3, 2004 to August 24, 2007.
  • A character/outfit gallery exists for Sam’s clothes, but the snippet I found does not specify the underwater wetsuit scene you described.

Best match

Based on the available episode data, the safest answer is that this was not a distinct recurring “season event,” but a scene-level costume appearance somewhere within the show’s run rather than a clearly labeled standalone underwater episode.

Quick note

The episode index I found is strong on dates and season counts, but not detailed enough in the available snippet to pin the wetsuit/scuba scene to one exact episode title.

If you want, I can next narrow it down by episode-by-episode scene matching from the episode list and character outfit references.