Pool Party - S1-E2
Other mistake: After Cleo transforms into a mermaid, her wetsuit doesn't disappear for some reason.
In Too Deep - S1-E23
Other mistake: When Miriam tells Zane she will give him the necklace for a kiss, she said "I will give it to you." But then when she throws the necklace in the water, she said "I didn't say I would give it to you."