Targeting 3- to 6-year-olds, the series explores the world's many mysteries above and below water in a unique and entertaining way.
Its characters include:
- Secret Agent Fishtronaut, a fish who wears flying armour to survive and interact with beings outside water.
- Marina, a human tomboyish girl
- Zeek, a monkey
- Billy and Mac, twins and innocent trouble-makers.
Fishtronaut has examples of:
- Action Girl: Marina, but the action is limited to searching for more clues in the park.
- Balloon Belly: When Zeek eats too much of anything. Happy Plumb also gets one, always.
- Captain Obvious: While targeted at 3- to 6-year-old children, sometimes it goes too far.
- Averted, in a lot of mysteries: Even adults can't solve the mystery before other clues are dropped.
- Catch-Phrase: Whenever they solve a mystery.
- Crazy-Prepared: Fishtronaut has anything you can imagine within his little armour.
- MacGyvering: Sometimes Fishtronaut pulls some tricks from his suit.
- Mobile Fishbowl: Fishtronaut's suit is full of water.
- No Fourth Wall: The characters always invite the viewers to help open the "pop" ball containing the initial clues.
- Talking Animal: Almost the entire crew. The only recurring humans are Marina, her uncle Dr. Green and the twins.
- Tomboy: Marina dresses like a boy, although she has prominent lipstick lips.