You could try going to www.veoh.com , once you are there, type in on the search box : 'H2O just add water episodes' and you can watch loads of episodes you haven't seen, because there are pages of them,and they are most likely to have the third episode. Hope this helps! :-}
this site here has most links to episodes of season 1 and 2, just scroll down til u reach them: http://www.sidereel.com/H2O:_Just_Add_Water but they do not have all, just most, lol. im still looking for episode 18 of season 1 and episode 14 of season 2
If you want to watch H2O just add water (fabulous show) online then just go to TeenNick.com and go to shows and look for H2O, once you find it go to their page and click on videos. It'll have all sorts of random videos and episodes that you might have missed.
The Surf the Channel link in the Related Links below has all episodes (free)
You can find it on YouTube of you search "H2O Just Add Water Season 3 Episode 1 Part 1".
at http://www.yidio.com/show/h2o-just-add-water
nick.com
just watch it on youtube
They are currently showing season 2 on channel 10 or can watch the episodes on YouTube.
i think through a link on http://www.yidio.com/show/h2o-just-add-waterthere are links to many h2o just add water episodes @ http://www.yidio.com/show/h2o-just-add-water or go to http://www.vbox7.com/ and type in h2o just add water then the season x episode number in the search box and press enter. e.g search for h2o just add water 2x13 or just search for h2o just add water and look through the pages. Those links have worked fairly well for me. If you have any trouble send me a message to me-Beckstar1122 and ill try to get back to you in a day or two.
You can watch H2o Just Add Water on netflix, dvd, or hulu.
There are loads of sites just try Googling 'watch h20 just add water online' and take your pick
Hulu.com
you can watch i think most of them online athttp://www.yidio.com/show/h2o-just-add-water
watch online through http://www.yidio.com/show/h2o-just-add-water
You can watch it on Hulu.com/h20-just-add-water
through http://www.yidio.com/show/h2o-just-add-water i think
http://vbox7.com/search/?offline=1&vbox_q=h2o+just+add+water&page=4
If you are in England you can watch h20 just add water on nickelodeon or you can watch it in youtube just tipe down h20 just add water season 3
i watch it on netflix but youtube.com will work also.
H2O: Just Add Water can legally be watched via Hulu and DailyMotion.
Search: H2O_ Just Add Water 1x14 Suprise - Veoh - Video Search