She had no idea the rule was she would have to swim home. Then she learned there might be a way out of her dilemma.
For a blowjob she gets a life preserver. She definitely wants that as it's a long way back.
For a suck and fuck, she gets a tow rope attached to the life preserver. That would get her back sooner. But she's wondering if he'll let her stay onboard all the way back if she gives him her ass as well.