Here's the scoop per the Frequently Asked Questions section of the Couples website:
Do you offer day passes for friends staying in the area?
Yes we do, however Couples Resorts limits the number of day passes sold. If you are planning to get married at the Resort please consult our Weddings & Honeymoons FAQ to learn more about it.
There are 4 types of passes.
Wedding Ceremony Only Pass – USD $50 per person
Half Day Pass [10:00 am - 6:00 pm] – USD $100 per person
Full Day Pass [10:00 am - 11:30 pm] – USD $200 per person
Evening Pass [6: pm – 1:00am] – USD $100 per person
I assume that you are cruising into Ocho Rios for the day? If so, be aware that CSS and Tower Isle are only about a 10 minute cab ride from the pier.
Bargain with the driver accordingly because they will try to charge you a rdiculous amount of money thinking that you don't know the distance of the resort or location from the cruise ship pier. Also, bargain with the driver for return trip back to the pier as this will make your total price lower. Important..pay each way separately. Give him a time for a return and he will be back knowing that he will have a fare..... Been there done that. Good luck!