"I've got a bit of a surprise planned," you said and looked around with a smile. "But as empty as this beach is I think that we should swim out a bit before I show you."
Lauren gave you a skeptical look. "This suit isn't really made for actually swimming." She indicated her bikini and pulled at the straps to emphasize.
"So one of your boobs falls out," Amber said with a roll of her eyes. "It's not like it won't be anything we haven't seen before."
"I can't really swim all that well," Molly said. She was giving the ocean a look while pinching her lips together.
"Don't worry," you said. "I wish that we could all swim as well as Olympic champions." You shudder for a moment as new knowledge forces its way into your head and a look confirms that the girls are doing the same.
"Whew," said Lauren. "Fine, let's all swim out and figure out what's in store for us." She led the way down to the water and the other girls followed. You eagerly brought up the rear, watching the four sets of swaying hips in front of you and the nubile asses that they were framing. Soon you were all in the water and swimming out with easy practiced strokes. By the time you signaled to the others to stop you barely felt tired.
True to Amber's prediction one of Lauren's breasts had slipped out while she was swimming and she fixed her swimsuit while asking you, "Ok, so what's the big surprise."
You smiled. "I wish you four girls were mermaids." All the girls stared at you with shock before they suddenly all threw their heads back. Loud moans came from Lauren and Molly while Amber and Veronica were busy feeling themselves up. Apparently the transformation felt pleasurable as the looks on the girls faces were comparable to when you were having sex with them. As you watched both Lauren and Amber's bikini bottoms floated to the surface, shredded. A quick dive under water showed that all four girls now sport fish like mermaid tails. Each had, through some process, gained the colour of their swimsuit and you watched as Lauren ran her hands along her red tail in wonder. Suddenly a second change hit the girls as their breasts jumped up a few cup sizes with each girl making an audible grunt as it happened.
Lauren and Amber were now completely naked while Molly and Veronica had only the tattered remains of their suits clinging to their waists. Each now sports a pair of breasts the size of their head and they're all looking at you.