Before you could react to the shocked look on Lydia's face, something grabbed your ankles and pulled you under the water and causing Lydia to fall from your arms. You struggled, trying to free your legs which seemed to be held tight. So tight in fact that you could feel your transformation begin, your legs merging together and ripping your pants downward from your crotch.
Lydia was shocked to see Monica was a mermaid. And not just any mermaid - an octopus mermaid, like Ursula. The thought crossed Lydia's mind it was so appropriate that Monica's mer form was of a hateful witch. Then she was tumbled in the water, her boyfriend pulled away. Before Lydia could even react, something grabbed her weakened legs and held them tightly. What last ounce of willpower was holding back her transformation was lost as Lydia felt her legs rapidly merging together and her feet flattening out into a tailfin. Her mermaid secret would be revealed to half the senior class. Still in her prom dress, Lydia struggled and realized one of Monica's tentacles had grabbed her and another had her boyfriend. Monica was holding both of you underwater, seemingly intent on drowning you if she could. Lydia struggled for the surface and managed to get her head out of the shallow water.
Monica saw her rival gasping for breath. "Who's laughing now, Lydia? The genie told me I could get my revenge on you!"
Genie? Lydia's mind raced: had Monica made a wish with the transformation genie too? Then Lydia was pulled under again. Twisting and kicking with her powerful tail, she managed to slip free and make for the edge of the pool. She coiled her mermaid tail like a spring and pushed off the wall for maximum acceleration before kicking with all the swimmer's might she possessed. A tentacle brushed by her, but Lydia was faster than Monica - as she had been before they were both turned into mermaids. Lydia shot across the pool, driving her shoulder into Monica's abdomen. This caused Monica to lose her grip on Lydia's boyfriend who immediately went to the surface for air. His pants were in tatters, his transformation to a merman now complete.
Meanwhile, the partygoers around the pool stood in shock at what they were seeing.