In the dimly lit cabana, the siblings' breaths grow heavy with anticipation. The sister, her heart pounding, reaches out to trace the outline of her brother's cock through his swim trunks. He gasps, his body tensing, then relaxing as he gives in to her touch. She teases him, her fingers expertly stroking him until he's rock hard. He, in turn, explores her body, his hands roaming over her curves, pausing to tease her nipples into stiff peaks. Their bodies press together, their hips moving in sync, simulating the act they both crave. Their moans fill the cabana, a symphony of their shared desire, until they can't hold back any longer, and they give in to their taboo lust.