Here’s the final part… this I had to take some liberties to figure out what was going on here.
H2O season 3
Epi 1 The Awakening : February 7-8th, 2008
(To be fair in real life the 7th is a New Moon not a full moon as that’s on February 21st. I really don’t care for the most part, but due to the 7th being mentioned in-universe to be a full moon towards the end of series)
Epi 4 Valentine’s Day : Feb 13-14th, 2008
(I honestly think they didn’t know what trigger the tentacle until much later given what Cleo says about school being weeks away is just wrong and the episode order between 1-4 is that the second was meant to Valentine’s not Jungle Hunt even if Bela’s crush wasn’t clear at first to them and to drag Will away on the island away from the Moon Pool)
Epi 2 Jungle Hunt : February 20-21st, 2008
Epi 3 Keep Your Enemies Close : February 27 - 29th, 2008
Epi 5 Big Ideas : March 5-6th, 2007
Epi 6 Secrets & Lies : March 12-15th, 2008
Epi 7 Happy Families : March 20-21st, 2008
(this is an interesting placement but hear me out in QLD their Easter break is Mar 21-24 in 2008 and makes perfect sense when going into the next episode as Don mentions the girls to study as their first trimester at school is nearly up which ends in April)
Epi 8 Kidnapped : March 22-23rd, 2008
(Full moon on Saturday 22nd)
Epi 9 The Sorcerer’s Apprentice : March 29 - 30th, 2008
(Will mentions that they need to study)
Epi 10 Revealed : April 5-6th, 2008
Epi 11 Just a Girl at Heart : April 12-13, 2008
*the next full moon is April 20
*out of universe a month has passed from epi 12 and 13, but it is quite common separating the autumn first half air-dates of the season from the spring return with the 2nd half. But however the internal timeline of the show is does not support this since I had work back-wards to front and with research of the QLD school year in 2008. As such several months have had to passed from episode 11 to epi 12, plus the graduating class of the 2008 school year is in mid-late November being the 14th til the 21st. Also from April to August is only four months
Epi 12 Crime & Punishment : Aug 18th. 2008
(this episode marks Rikki’s birthday. Due to Bella’s comment of Rikki’s present to be an early Christmas gift it could be thought to be a few months before December)
Epi 13 To Have and To Hold Back : August 25 -26th, 2008
(this holds up really well with the scholarships for the senior class being around January & September, and most American colleges start in mid-late August or early September. We learn from Lewis that he applied earlier in the year but didn’t think that he would get picked for the scholarship)
Epi 14 Mermaid Magic : Sept 1-3rd, 2008
Epi 15 Power Play : September 8-10th, 2008
Epi 16 The Dark Side : September 15th, 2008
(full moon on Monday 15th)
Epi 17 A Magnetic Attraction : September 16 - 17, 2008
(several weeks cannot have passed between episode 16 and episode 19, maybe two weeks at most maybe even just shy of two weeks at nine days)
Epi 18 Into the Light : Sept 18-20th, 2008
(this episode either starts on the 17 or 18th of September since most episodes are normally one week apart)
Epi 19 Breakaway : Sept 24-25th, 2008
Epi 20 Queen for a Day : Oct 1-3rd, 2008
Epi 21 The Jewel Thief : October 8-9th, 2008
Epi 22 Mako Masters : October 15th, 2008
(full moon on Wednesday 15th, this specific full moon happens during the day and during final exams. The girls are given a projection from the moon and tentacle about a comet, however the projection is cut off by Zane & Will coming to help)
Epi 23 Beach Party : October 30-31st, 2008
Epi 24 Too Close for Comfort : November 6 - 8, 2008
Epi 25 A Date with Destiny : November 10-13, 2008
(the end of this episode leads directly to the next presumably having one day apart. The girls end up do research on the Eva’s comet, figuring out why they were chosen and swim to the Moon Pool when the wall gets blown up by Sophie and Ryan. Cleo discovers that the first full moon of the season was on February 7 as that was when Eva’s comet entered the solar system)
Epi 26 Graduation : November 13-14th, 2008
(full moon on Thursday 13th. Since the Moon Pool was destroyed by Sophie & Ryan, so the girls have to use their powers to creating the Tower of Light to repel the comet. Graduation for QLD is around November 14-21st, so this placement makes absolute sense and many months have passed between the first & the second half of the season)