Trivia: H2O: Just Add Water
- Dawson Casting: Averted in the first two seasons as the three leading actresses were still in high school, but the gap between Seasons 2 and 3 left them playing high school seniors while they were 20/21 in the final season.
- Hey, It's That Voice!: In the Japanese dub, Charlotte is voiced by Ema Kogure, who voices Caren in Mermaid Melody Pichi Pichi Pitch.
- No Export for You: In the US, the last half of Season 2 and the entire third season were held up substantially. The show ended half-way through Season 2 during re-airings in 2008. When TeenNick began re-airing the series in 2011, the remaining episodes still weren't being aired - instead cycling through the same aired episodes again and again. Finally averted on January 16, 2012, where the final thirteen episodes of Season 2 were aired in a TeenNick marathon leading into the US premiere of Season 3. (3 Years after the UK aired the 3rd season.)
- The rest of the world, including its native Australia, didn't get the 3rd season until 2010, whereas the UK got it first in 2009.
- Retroactive Recognition: Emma's Season 2 Love Interest, Ash, became the True Seeker.
- Star-Making Role: For Claire Holt and Phoebe Tonkin.