Well, I personally watched it on 'Hulu'. It was for no charge at all but the only problem was that there were a lot of commercials :)
nickelodian or internet
at http://www.yidio.com/show/h2o-just-add-water
http://vids.tv/H2O-Just-Add-Water/tv/season-2/episode-12-Monster
just watch it on youtube
At www.veoh.com
at http://www.yidio.com/show/h2o-just-add-water
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 find h2o just add water on DVD at the shops but you have to buy it You can find h2o - Just Add Wather season 1, episode 2 and first 10 episodes from season 3 at: http://www.gtv33.com/2009/08/watch-h2o-just-add-wather-online.HTML
through links on http://www.yidio.com/show/h2o-just-add-water
They are currently showing season 2 on channel 10 or can watch the episodes on YouTube.
through http://www.yidio.com/show/h2o-just-add-water