Amy was shocked by the sudden kiss. She had never been attracted to Lina before, and wasn't aware that Lina had ever been attracted to her. And yet the feeling of Lina's tail against hers, the feeling of Lina's lips against hers...
Lina broke the kiss and looked disappointed. "No?"
Amy wasn't sure what to do. She looked to Mark for his reaction and found him staring intently at the two mermaids. Lina followed her gaze.
"Mark, are you willing to share?" asked Lina.
Mark hesitated, trying to chose his words carefully. "If my mermaid girlfriend wants to have a threesome with me and her mermaid best friend, I'm not going to turn it down. But I'm not sure Amy is okay with this..."
Lina looked back to Amy who was fidgeting with her necklace. Amy nervously glanced back and forth between Lina and Mark. Lina cupped her breasts and fondled them, trying to entice Amy. Amy stared for a moment then moved closer to Lina. She slowly brought her hands to Linda's face and brought their lips together for the second time. There was not mistaking it: Amy liked the feeling. She broke the kiss and said "Yes" then kissed Lina again.
Lina wrapped her tail around Amy's then untied Amy's bikini top and let it float away. Now the two mermaid's bare breasts pressed together. Lina undid Amy's skirt and let it float away as well. The two mermaids reveled in the sensations of their bodies pressed together then Amy remembered they were forgetting someone. She pulled her lips away from Lina's and turned to find Mark had removed his underwear. She reached her hand out to Mark who eagerly took it, drawing close to the two mermaids.