<Tr> <Td_colspan="6"> Charlotte takes control of the planning for Lewis' birthday party, and refuses to let any of the other girls help . Rikki, fed up with Charlotte's intrusion into what was once their close - knit group, decides to exclude herself, and leaves to spend more time with Zane . Meanwhile, at the boring birthday party that Charlotte has organised for Lewis, Charlotte jealously locks Cleo and Emma in a flooded storage room, where they are left trapped as mermaids . Their secret is threatened when Ash hears them in the storage room and tries to unlock the door, only for Zane and Rikki to arrive in time to help . Zane leads Ash away whilst Rikki uses her powers to dry the girls . Realising what Charlotte has done, the girls then organise a party boat to come and take Lewis from Charlotte's terrible party, and then tell Charlotte that she is not one of them any more . </Td> </Tr> <Tr> <Th> 51 </Th> <Td> "Sea Change" </Td> <Td> Colin Budds </Td> <Td> Robert Armin </Td> <Td> 14 March 2008 (2008 - 03 - 14) </Td> <Td> 225 </Td> </Tr> <Tr> <Td_colspan="6"> Charlotte's short - lived friendship with Emma, Rikki and Cleo is over, and she forbids Lewis to talk to them . When Cleo shows concern for him, Charlotte lies to her, saying that Lewis willingly gives Cleo the cold shoulder because he doesn't care about her any more . A fight leads to Charlotte taking Cleo's locket, and when Lewis does nothing (believing that Cleo gave the locket to Charlotte, because it was her grandmother's), an upset Cleo is convinced that Lewis is on Charlotte's side, and leaves a phone message for him (which he doesn't hear, as Charlotte has stolen his phone), about how he has abandoned her and wants nothing to do with her, before running away from home . When Lewis eventually hears Cleo's message, he breaks up with the venomous Charlotte, and races after Cleo . Meanwhile, Cleo is being hunted by a pack of sharks, who can sense that she is weak . Lewis arrives just in time to save her, and the two of them get back together . </Td> </Tr> <Tr> <Th> 52 </Th> <Td> "Unfathomable" </Td> <Td> Colin Budds </Td> <Td> Chris Roache </Td> <Td> 21 March 2008 (2008 - 03 - 21) </Td> <Td> 226 </Td> </Tr>

H2o just add water what episode does zane find out